Incompatible Programming Must Be Addressed When Installing Used Components

By Chris Adams, Diagnostician

adams-chris-2Chris Adams started with Certified Transmission in 1986 as an R&R technician, and currently works as our Diagnostic Trainer. His current duties involve training and advising our retail diagnosticians, as well as assisting in the research and development of our remanufactured products. He is also holds ASE Master and L1 certifications.

We had a local general repair shop bring us a 2014 Jeep Grand Cherokee 3.6L V-6 engine equipped with a ZF 8 Speed (845RE) transmission; they had just installed a “rebuilt” transmission that was sourced from a salvage yard. The customer’s stated concern was, “The place that built the transmission just said it needed to be programmed.” Needless to say, we knew that this was going to be an adventure.

When we began our evaluation, we found that there were a bunch of ‘U’ codes for invalid data received from the TCM, but we did not get that far into it since the customer was adamant that they just wanted it programmed and did not want us to do any kind of diagnostic. After all, it was a “rebuilt” transmission, so what could possibly be wrong? I wish I knew how to convey sarcasm in the written word; I can do it in person pretty well.

We do a lot of programming in our shops and we have equipment and software to cover almost all automobile manufacturers in-house, with the exception of a few higher-end European vehicles that we do not see on a daily basis. Each of our locations has a laptop that is specifically setup for programming plus a J2534 device, but we also have a variety of OE tools also. For this vehicle I grabbed the Witech tool and proceeded to go through the reprogramming process. There was an updated calibration available so I went ahead and flashed the TCM to the updated part # of 68234057AA, and everything went fine. Programming completed with no errors or warnings, or so I thought.

After programming, I always go back and clear codes from all modules and also look at the reports that WiTech will generate, but specifically the ECU data. This is where I saw some discrepancies. Figure 1 is the TCM data, and it is here that you can see that the current VIN and original VIN do not match. The one that ends in 2111 is the correct VIN for the vehicle.

FIG 1

Figure 1

Needing to know what this transmission came out of was my next step. Running a VIN decoder (Figure 2) showed that this unit was pulled from a 2015 RAM 1500 with a 5.7L engine.

FIG 2

Figure 2

What? Dealing with the 8 speeds is fairly new to us and we have not seen that many in our shops, but I was pretty certain that an 8HP70 that was behind a 5.7L V8 would not work properly in the place of a 845RE mated to a 3.6L V6. To try to make a long story short, the used, er…whoops, “REBUILT” transmission did have some work done to it, but they either installed a complete valve body or at least the TCM from another vehicle. While it is possible in certain circumstances that a used TCM can safely be installed in another vehicle, the calibration or ECU part # has to be for that same vehicle as neither the OE WiTech tool nor the J2534 programming software will allow you to change the calibration # or the VIN in the TCM. It will always have a current/original VIN mismatch when looking at ECU data, but when this is only in the TCM, it does not seem to set a code or cause any other issues (I must say that this is from very limited data, and might not be true in later model vehicles 16 & up; this example was a 2014 MY vehicle). Bottom line is that this would never work as-is.

The second part of this story starts after we installed a NEW complete valve body from FCA into this Jeep to make things match. Our WiTech was not available so I used the J2534 tool to program the new TCM. Here is where I want to direct your attention, because if you are not paying attention this is where you could get into some trouble. You probably can’t read the writing in red on that screenshot, so what it says in Figure 3 is this:

NOTICE: There is more than one flash to select from for this ECU. Ensure that you have selected the correct one in the drop down box before you initiate the flash. Note that the contents of the Service Bulletins table change according to the flash selected.

FIG 3

Figure 3

The “FLASH ECU” button can be pushed, but the 68225555AF calibration that is listed is NOT correct for this vehicle! You must select the correct file from the drop-down box, and the correct Cal file is shown in Figure 4 of 68225561AG in the topology view.

FIG 4

Figure 4

In the next set of images you will see screens that you would encounter during the programming process. Make sure you get all the way to “Flash Complete”, and the “OK” button is highlighted.

FIG 5

Figure 5

FIG 6

Figure 6

FIG 7

Figure 7

FIG 8

Figure 8

After you get done programming, as you see in Figure 9, the “FLASH ECU” button is still there.

FIG 9

Figure 9

Even after programming it takes a bit of time before that goes away. The VIN and the correct calibration are shown above it, but before programming the VIN was all question marks and asterisks in the part # line. When I clicked the topology view in Figure 10, the “Flash” button went away and the TCM displayed as “Current”.

FIG 10

Figure 10

I do want to add that this process is specific to the J2534 programming process; if you are using the OE WiTech tool, it will pull the correct calibration file by the VIN, and with the blank TCM part number, you will only have the one option. We can only hope that the aftermarket software can start working more like the OE software does as time goes forward, but for now we need to work cautiously when dealing with the 8, 9 and 10 speeds that will be coming in our doors.

You can look up the correct calibrations on the Tech Authority website without a subscription, but you have to know where to look. Here is the link:

https://kb.fcawitech.com/secure/chrysler-scan-tool-flash-availability-document-775.html

At the bottom of the TA homepage there is a link called “Related documents and links”. If you click on that, it will show several other links that you can get to without a charge, and one of them is the “Flash availability” PDF file.

It will be challenging in the coming years dealing with used components that have vehicle-specific programming within the modules inside of them. Since the salvage industry uses part numbering standards such as “Hollander”, it lumps incompatible software with compatible hardware. We must always ask questions about the origins of these components as that will help us determine how we can proceed to solve the customer’s vehicle problems.

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Resistance Checks Don’t Tell The Whole Story

By Troy Hopp, Diagnostician

hopp-troyTroy has been in the automotive repair industry his entire career and has been with Certified Transmission since February 2010. He has an Applied Science Degree in Automotive Technology from Western Iowa Tech and is an ASE Master Certified Technician.

About a month ago a customer came into our shop with a 2008 Chrysler Town & Country equipped with a 4.0 liter V6 engine, and a 62TE transmission. He was complaining that it had a whining noise, and sometimes it would not shift and seemed to stay in the same gear. When the vehicle was hooked to the scan tool it had a code for the overdrive solenoid control circuit (P0760). The fluid was at the correct level and smelled like normal fluid, however, it was dark purple indicating possible metal contamination.

I took it on a test drive and verified that the whine noise was definitely coming from the transmission, but it shifted and operated ok. There were no other DTC’s in any other modules except for the TCM and the visual inspection did not reveal anything that needed attention. We also do a battery and charging system test with a Midtronics analyzer which also passed all the test protocols. The next step was to get the customer’s permission to remove the transmission pan for inspection, which the customer granted so we then proceeded with the inspection. Upon pan removal, severe fine metal contamination was verified on the bottom of the pan, along with large amounts of metal in the filter when it was cut open. I think we found the cause of the noise!

The customer decided that with 160,000 miles it was best to replace the entire transmission with one of our remanufactured units. We replaced his transmission, reprogrammed the powertrain control module, and used a “hot flush” machine to clean out all of the metal out of the transmission cooler and lines. I cleared the code and test drove the Town & Country for about 30 minutes with both highway and city driving. The whine was gone; it shifted perfectly and did not set any codes, so I felt that it was safe to presume the code was caused by a faulty overdrive solenoid.

We always inform our customers to return to the shop in 15 days to perform a free follow-up evaluation so we can make sure that there are no leaks, codes, or any other problems associated with our repair work. The customer returned about two weeks later stating that the transmission was nice and quiet now, but that it still got stuck in second gear one time since we replaced his transmission. I scanned the Town & Country to find that the same P0760 overdrive solenoid code was stored. So we then had to ask the customer to drop off his vehicle again so we can figure out what was causing the code to reset, we put him in a rental car so we could continue diagnosis. At this point I figured it was safe to assume the solenoid itself was not the problem since it was replaced with the transmission, therefore it could only be a bad overdrive solenoid control wire or an intermittent internal failure of the powertrain control module.

The powertrain control module never failed to activate the overdrive solenoid during the solenoid on/off testing with our scanner; therefore, I did not think the problem was with the driver in the powertrain control module. I then directed my attention towards the yellow and gray overdrive control wire from terminal #1 of the powertrain control module, to terminal #19 of the transmission solenoid connector (FIG 1).

FIG 1

Figure 1

Since I have been burned before by using resistance checks, we try to only use voltage drop testing unless the component is completely inoperative. I back-probed terminal #19 at the transmission solenoid connector in preparation for a voltage drop test. I had battery voltage until I activated the overdrive solenoid with the scanner, and 4 volts were indicated on my volt meter, indicating that the solenoid was only getting about 8 volts of the 12 volts needed to properly operate the solenoid, however it was apparently enough to get the job done most of the time. Was the voltage drop on the B+ side, or the control side of the circuit? I probed on pin 21 for the 2-4 solenoid, and when activated the DVOM showed about .10 volts indicating a good circuit which confirmed the integrity of the B+ side of the circuit.

A closer inspection of the wire revealed that only three or four strands of copper at the terminal of the transmission connector were making contact (FIG 2). A small tug on the wire was all it took to completely break it. This is a perfect example as to why a simple ohm check of the wire is not a good enough test in this case; an ohmmeter test would show normal resistance indicating no problems with the wire, even with only three strands of copper holding it together. The real issue was that the damaged wire could not support the amperage needed to properly activate the solenoid at times, especially when hot.

FIG 2

Figure 2

I did get a little lucky during diagnosis. I wanted to look at the connector just to make sure that the R&R technician had the connector fully locked into position, which it was. However, after checking the connector the problem went from being extremely intermittent to setting the code pretty easily, so that did narrow down my focus on where to look for the problem. Happy accidents can be helpful in cases like this.

I found a transmission solenoid connector pigtail that we use for testing and robbed one of the terminals/wires out of it, and installed it into the Town & Country’s solenoid connector. A quick voltage drop test showed that the solenoid was now getting use of all 12 volts being supplied to it. I cleared the code and test drove the van another 30 minutes and no codes were reset. We sent the customer on his way and he has not been back, now having both of his initial complaints resolved. The whine noise was easy to figure out, but the intermittent code P0760 in this case took a little extra effort to diagnose.

Now wouldn’t you know it, within one week of repairing the P0760 in the 2008 Town & Country, a 2010 Chrysler Town & Country, also equipped with a 4.0 liter V6 and a 62TE transmission, came to our shop with a complaint of a check engine light, intermittently not shifting, and staying in second gear. This vehicle’s transmission fluid level was full and in good condition, however. I scanned it to find a 2-4 or 2C solenoid control circuit code P0755. I thought, “What are the chances that this van had the same problem as the 2008 Town & Country I repaired a week ago?”

I decided another voltage drop test was in order. I back-probed the solenoid connector at terminal #21 dark blue and yellow wire for the 2-4 solenoid control. I activated the solenoid with the scanner, and my voltmeter read 5 volts indicating that the solenoid was only getting 7 of the 12 volts needed to make it properly operate. I barely tugged on the wire, and it snapped right off (FIG 3); it was the same exact scenario as the wire on the ‘08 Town & Country a week ago.

FIG 3

Figure 3

I replaced the terminal, cleared the code and test drove the van. It shifted fine and no codes were reset. Who says lightning can’t strike twice?

Improvise And Accept The Difficult Jobs

By Mike Greer, Diagnostician

greer-mikeMike has been with Certified Transmission since 1996, and been in the industry since 1987. He is an ASE master Technician and has served as a Master Builder for the company in the past.

My article is going to be a little different this time, and geared more toward the R&R technician. It’s about a car that came to us from a large local dealership that has 13 different locations, and works on 14 different makes of vehicles. The subject vehicle is a 2014 Mini Cooper Countryman AWD, with a 6 speed manual transmission. Mini is one of the only makes that this dealership does not sell; being in good standing with this dealership, they brought it to us to perform the repairs needed and get their customer back on the road. With very little information available on the internet for removal and installation, we did think about purchasing a short term subscription to BMW/Mini service information, but hey, it’s a clutch job, so how hard could it be?

The vehicle needed a clutch replacement which seemed fairly straight forward, so we jumped right in to get this back to the customer as quickly as we possibly could. We ended up needing to call the local Mini dealer and order OE parts since there was limited availability of aftermarket clutch parts. This vehicle was equipped with a Dual Mass Flywheel set up, so with this knowledge we started the removal process. Remove the air box, get the battery out of the way, removed the bell housing bolts, etc. all from the engine compartment, then raise the vehicle up to start taking off the front two wheels. Also, a good trick we found was taking the driver’s side headlight out, and removing the front bumper cover as this gave us better access to the transmission and it was removed fairly easily and quickly.  We felt that this added step saved us a lot of time not trying to fight getting access in such a tight area. After this, things started to get interesting.

This is a photo of the rear driveshaft where it attaches to the PTU.

Figure 1

Figure 1

We discovered a TSB that referred to this attachment. It told us we needed a special tool to get it apart and it is a large wrench end that attaches to a long half-inch extension to get it apart.

Figure 2

Figure 2

We obviously did not have anything even remotely close to this tool, nor did any of our other shops in the area. Calling the local dealer, we could buy the special tool, but it was a little over a week out to get one. Upon further investigation we decided the PTU possibly could come out with the driveshaft still attached.

After unbolting the PTU and separating it from the transmission we found the next road block: the intermediate shaft in the PTU is too long to get the PTU removed without it hitting the back of the engine. We started looking over how everything is put together, to see if we could still make this work. While looking, we found a snap ring around the passenger side axle.

Figure 3

Figure 3

With that snap ring removed (and with the help of a sharp, new pry bar, and hammer) the axle popped out of the PTU allowing us to remove that PTU with the driveshafts still attached. This might not be the easiest method, but it worked and we transmission technicians always seem to find a way to get ‘er done!

This is a picture of the PTU on the floor with the attached pieces mentioned.

Figure 4

Figure 4

After getting these parts out of the way, we could then remove the transmission. As a side note, if you do need to service the driveshaft of any reason, you will need that special tool I mentioned previously to get the driveshaft separated from the PTU. Back on track, everything else went very smoothly and we finished replacing the clutch, flywheel and all associated parts. We put the vehicle back together, and then went for that final test drive.

Some additional notes: make sure the correct parts are ordered for these vehicles, and the labor charge is sufficient. This was a very big clutch job, and very expensive as the total bill came out to be around $2700 retail. Make sure if it is supposed to have a Dual Mass Flywheel (DMF) it gets replaced. Trying to cut corners on a job like this does not do you or your customer any good. Not pricing this job out correctly up front can mean one of those phone calls that you do not want to make after the vehicle is disassembled; it can mean a very large pricing difference, as well as correct fitments.

This is where the LUK clutch catalog or online catalog can come in handy. With this catalog, you can check to see if they offer the DMF set up for your application. LUK offers a much more affordable option for your customers versus the OE parts (for many applications, LUK or Valeo are the OE supplier), so you will save your customer quite a bit of money if your application is available from them. In their catalog, you can also find the “flywheel options” if you are sending out the flywheel to be surfaced, as the information in the catalog will tell you if it is a flat, step, DMF (cannot be turned), or cupped style. It will give you dimensions and measurements so you can make sure the flywheel will still be in spec after having it surfaced.

In closing, I just want to say if you get one of these all-wheel drive Mini Coopers in your shop, do not turn it away for fear of being too complicated. The job ended up being fairly easy, the shop made good money, and the R&R technician made good time on it. Next time he will be able to do it even faster, and have an even better turnaround time.

Verify Data Before Condemning Components

By Dana Deeke, Diagnostician

deeke-danaDana joined with Certified Transmission in 1991. Dana has worked in all positions at the Lincoln location, starting as an R&R technician and is now our current diagnostician for our Lincoln, NE facility. He enjoys car racing and spending time with family and friends.

Every now and then we run across a vehicle that has a concern we have seen many times before and we almost automatically try and diagnose it by memory; it’s almost like a reflex we develop over time. Of course as we all know too well, this can lead you down the wrong path if you stray away from complete testing and verification.

The subject vehicle is a 1999 Chevrolet Tahoe. It came to us on a wrecker, as the customer was not comfortable driving it to us. The concern was stated as harsh shifts and a check engine light on. The vehicle was brought into the shop and the fluid level and condition were checked. The fluid level was full but had a strong burnt odor, and was discolored. A quick scan of the computer revealed code P1870, “transmission component slipping”. We now knew what was causing the check engine light and harsh upshift concern. From here I left the scan tool attached and went for a short road test to try to further verify the concern. Just as the code had indicated, the scan data showed the TCC turning on, the duty-cycle start to ramp on (eventually getting to full duty-cycle), and the TCC slip parameter still showed an abnormal level of slip.

At this point it appeared that the PCM was commanding the TCC on and the duty-cycle was increased in response to the slip that was sensed, however the RPM was not coming down as expected and the P1870 would then set. It appeared that we may have had some sort of mechanical failure of the torque converter clutch system. We do see that from time to time. This is where some more questions for the customer can help. Whenever possible, I like to try to find out the history of the vehicle I am working on, as it can lend clues to the failure. In this case, I was glad I was able to find out some good info.

This truck had had the transmission replaced not too long before it came into our shop. As we learned more from the customer, it became clear that there was a pattern present. By now you may have guessed that the previous failure also involved the P1870 code! It was time to look at this issue a little more closely.

I looked around through TSBs and found all the typical failures you see with this code. I also ran it past the guys in our technical division. They get calls from all kinds of shops and can be a great resource for information. Everything I looked at pointed to a mechanical failure, but I was starting to doubt this with the information I found out about the previous failure, and the same code being present. Could two transmissions have the same failure? Absolutely possible, but sure seemed unlikely.

I pulled up the wiring diagram and connector views for the PCM. The PCM is located on the driver’s side fender well so it is easily accessible (FIG 1).

FIG 1

Figure 1

I decided to try to verify that the on/off solenoid was working and being commanded to work. Both the TCC on/off solenoid and the TCC PWM solenoid are located on the valve body on this transmission and would require dropping the pan to access them, I decided to start my testing at the PCM (FIG 2 & 3). Connector C1 (blue) at the PCM contained the TCC on/off solenoid control on pin 10, which was a tan/black wire. C2 (red) contained the TCC PWM signal wire on pin 7, which was a brown wire (FIG 3). Checking from the PCM with a DMM I was able to verify that the signal was getting to the on/off solenoid, and that the solenoid was indeed turning on.

FIG 2

Figure 2

FIG 3

Figure 3

Next I ran the vehicle on the hoist while watching the TCC data. I have used this strategy before with gear ratio codes to see if they would reset on the hoist without the weight and load of the vehicle. The PCM scan data showed TCC solenoid turning on, and TCC PWM solenoid start to raise the duty-cycle to full, just like on the test drive, but my TCC slip rpm was still high. That seemed strange, no load/full duty-cycle was showing as much slip as driving with a load on it. You would think if there were an actual slip, the degree of slip would be affected by the load, or lack thereof.

What about that PWM solenoid and the signal to it? Again I went to the PCM, this time commanding the duty-cycle while monitoring it with the DMM, there was no signal present (FIG 4)!

FIG 4

Figure 4

The PCM was showing scan data that made it look like everything was operating as it should be, but there was no actual signal coming from the PCM even though it showed otherwise on the data stream. It could recognize that the slip was not coming down with the duty-cycle going up, and would set the code. At this point it sure looked like we may have a failing PCM. I wanted a second opinion, so I relayed all the information to our lead tech, going over everything that had happened up to this point. He agreed that it sure sounded like the PCM had a problem so I decided to pull the trigger.

A new PCM was ordered, installed and programmed. Several test drives at highway speeds were performed, and the truck showed no TCC slip, and no codes returned. This is the first time I had run into this sort of thing causing this code and symptom, and I can see where it would be very easy to assume that the problem was inside the transmission. Given that everything on the scan tool looked good, countless other vehicles are fixed with a transmission when they act like this. I can only assume that the transmission had already been replaced for this reason once before. It’s always a good idea to verify that what the scan tool is displaying to you is actually what’s taking place. False information results in incorrect diagnosis.

Transmission Issue Creates Symptoms In Other Vehicle Systems

By Sean Mahoney, Diagnostician

mahoney-seanSean has been a member of the Certified Transmission team for five years. He is ASE-Certified and enjoys the challenges that come with diagnosing vehicle problems.

A while back we had a customer come into our shop stating, “The vehicle sometimes has a VSC (Vehicle Stability Control) error and won’t go past fourth gear, but today it seems fine.” The vehicle was a 2007 Lexus LS460 with 132,561 miles, and equipped with an AA80E 8 speed transmission and a 4.6L engine. As with routine diagnosis, I started with a road test, a scan of all modules, and an undercar inspection.

The scan procedure came back with four DTCs: P0771 (shift solenoid ‘E’ performance), P0796 (pressure control solenoid ‘C’ performance), and P2714 (pressure control solenoid ‘D’ performance). There was also an unrelated HVAC code stored. Because there were no VSC or ABS diagnostic trouble codes present, when the check engine light was illuminated the system was possibly turning the VSC system, but at this point it is too early to rule anything out.

On the road test I backed out of the parking spot and started on my normal route. At the first stoplight the transmission clunked into gear while coming to a stop, and when I accelerated I could tell the transmission was in a higher gear. Oddly enough, the vehicle would try to shift once in a while after taking off from a stop, but most of the time the transmission stayed in third gear.

fig1

Figure 1

As I pulled the vehicle into the bay door to do an undercar inspection and to finish my initial evaluation, I put the car in reverse and had a 5 second delay followed by a very, very hard reverse engagement. I tried to duplicate the delay a few more times with varied results, sometimes it went into gear with no issues and sometimes it had a hard delayed reverse engagement. Underneath the vehicle I checked the fluid (which was dark) and I noticed that the wiring coming out of the transmission connector looked oily. Even though the VSC light didn’t illuminate on the initial test drive, I could tell there was still a problem that needed to be addressed. Due to the oil-soaked harness and the solenoid codes it was time to recommend further testing. The customer agreed and left the vehicle with us to proceed.

I wanted to get as much technical information about this transmission (even if it was unrelated to my problem) before I went any further. I took a look at the diagnostic trouble code information and flow charts, and surprisingly the information for P0771 and P2714 directed me to start with P0796 (pressure control ‘C’ performance code) if all three DTCs were present. I started with a simple battery and alternator test, which the vehicle passed. Next, I raised the vehicle back up and proceeded to disconnect and inspect the transmission connector more closely due to the possible fluid weeping through. As I thought, the ATF was pushing through the connector.

fig2

Figure 2

fig2a

Figure 2A

Curiosity got the best of me and I unplugged the transmission harness, let the vehicle down and shifted between park and drive to reverse multiple times. Just as I assumed, I had a reverse engagement every time, albeit very firm and quick, as expected. I carefully disassembled the connector cleaning it with electrical contact cleaner (Deoxit D5), and dried out the connector socket at the transmission. I started next, with checking for B+ at the ECM connectors for the solenoids, next I removed the E6 and E7 connectors from the TCM and started with a simple resistance test through the solenoid circuits.

fig3

Figure 3

The specification for the SLT (P2714) and SL3 (P0796) solenoids (which are linear solenoids) is 5.0-5.6 Ω, and 11-15 Ω for the SR (P0771) solenoid which is one of the two on/off solenoids in the transmission. I found 5.6 Ω at the SLT solenoid and 5.5 Ω at the SL3 solenoid. Both were in spec, but the SR solenoid showed 47.3 Ω when checked. Next, I checked resistance from the transmission connector to the TCM connector to make sure my SR solenoid wiring wasn’t shorted to ground anywhere. I found .3 Ω from the transmission connector to the TCM connectors on all three solenoid circuits. I knew that the probable cause of my problem was the SR solenoid, but since I was already at the TCM and had my scope handy I wanted to see if I could watch the three solenoids before while getting the vehicle to act up.

fig4

Figure 4

When reverse was engaged the SR solenoid dropped from 12v to 0v which showed it was being pulled to ground as it should be. After removing the pan, the SR solenoid checked directly at the solenoid was 47 Ω. I conceived my recommendation: replace the SR solenoid and the internal wiring harness to address the customer concern and the connector leak.

Even though the case connector has plenty of clearance between the valve body and case, the valve body still needed to be removed to unplug sensor wiring above the valve body.

fig5

Figure 5

I removed the filter and unplugged the solenoids. Next, I removed the e-clip that secures the manual valve. There are 17 bolts that needed to be removed, and 3 different lengths used holding the valve body to the case.

fig4

Figure 4

The spring and check ball body above valve body need to be accounted for when going back in. After installing the harness and putting the valve body back in, I installed the new SR solenoid which checked at 13 Ω like it should have. One thing to note is that the transmission fill procedure on this vehicle is very specific and too long to include in this article, so if you work on one of these units be sure to refer to service information when setting the fluid level.

After getting the transmission filled up, checked and rechecked again, I was ready to see how this vehicle is supposed to normally drive.

fig6

Figure 6

The vehicle shifted great, and after a few long road tests I was confident that the original issue was addressed and repaired, so the vehicle was then delivered to the customer.

One month later the vehicle returned to me with the customer complaint of, “The check VSC light is on, but it is shifting okay at this time.” This time the VSC light was illuminated along with the check engine light. A quick code scan revealed a P0171 (system too lean bank 1), and C1201 (engine control system fault) which sets the check engine light and the VSC light. It’s usually never a great thing when a vehicle comes back, but in this case I could verify the transmission operation over a longer period of time and refer the customer to a shop that could address his engine-related codes.

I wanted to bring attention to this one because one of the issues that we have seen lately is other shops not spending time to look at all things related to a warning light. This nearly identical circumstance had happened previously where the customer took his car to a transmission shop with the VSC light on and was referred to a general repair shop because, “We don’t work on that stuff” prior to even hooking up a scan tool. The customer then goes to a general repair facility where he is told that’s a transmission problem and, “We don’t work on transmissions”, and then finally to one of our locations where the customer issue is finally repaired. You can see how frustrating this could be for anyone getting this poor level of customer service. The takeaway is to know and understand the various systems that are involved in your diagnosis, and how they relate to each other.

Heat-Damaged Harness Causing P1860 Code – 4L80E

By Randy Peterson, Diagnostician

peterson-randyRandy has worked for Certified Transmission for over twenty four years and is an ASE Certified Master Technician, including L-1. He has been in the automotive industry for over 30 years.

1999 Chevrolet C30 7.4L 4L80E

The subject vehicle that was fitted with one of our remanufactured transmissions 6 months prior showed up at one of our repair locations recently, with the customer concern of an intermittent bumpy 1-2 shift, and a low power lugging sensation along with a CEL on. While performing our initial evaluation, we found a P1860 code stored in history, but not current. During the road test the truck was working well with no clear signs of what set the DTC, but after several minutes of driving it then started to act up. The TCC was applying right on top of the 1-2 shift, but according to the scan tool data, was not being commanded on by the ECU.

To diagnose the issue, a wiring diagram and a code description were printed and reviewed; this is a typical circuit for a GM transmission. The fuse feeds power to the transmission shift and TCC solenoids through pin ‘E’ at the case connector, and the power then runs through the solenoids and back to the VCM. The VCM is responsible for grounding the circuit to energize the solenoids. The TCC solenoid in this application is a PWM type and the computer duty cycles it on to provide a smooth engagement. A comprehensive battery and charging system test was performed to make sure that there was adequate voltage for proper circuit operations.

With this knowledge I decided to first check to see if there was B+ at pin ‘7’ (brown wire at the C2 connector of the VCM) with KOEO. [FIG 1] If there wasn’t any voltage drop at that location I knew the circuit was complete with no opens or shorts to ground, and if there was a voltage drop I would start backwards from the VCM to look for an open/short in the circuit. There was B+ at pin ‘7’, so I hooked up my scope to test the circuit with the scanner using the bilateral controls and then drive the vehicle to see if the problem would occur.

FIG 1

Figure 1

I back-probed pin ‘7’ at the VCM to monitor the voltage with my scope lead, and then I put an amp clamp around the brown wire to monitor amperage [FIG 2]. Using the Tech2Win software to cycle the TCC solenoid, I could see the voltage drop to 0 and the current went to approximately 0.8 amps. The specification for the solenoid is 10-15 ohms. Using Ohm’s Law I could quickly see that the amp reading was close without pulling out my calculator, at least close enough that it would not trigger a code. Now it was time to run the cables into the cab and go for a test drive.

FIG 2

Figure 2

After driving a couple of miles the engine temperature was up and the TCC came on. The pattern was picture perfect. The VCM cycled the PWM solenoid and then completely grounded it to apply TCC fully. The amperage was what I was expecting to see [FIG 3].

FIG 3

Figure 3

It took quite a few more miles before the incident recurred. I took off from a stop, shifted to second and TCC was fully applied. I looked at the scope and saw that the voltage was very erratic but near zero, the amperage was at zero and the DTC also set. How could the voltage be at zero with the TCC is on, and there is NO Amperage going through the circuit? [FIG 4] Smarter men than I would know the answer to this right away. I just could not wrap my head around it at the time. Solenoid on, TCC applied, no current flow. I had to sleep on this one.

FIG 4

Figure 4

The next day Carman (shop Diagnostician) and I were discussing how there could be a completed circuit, the TCC solenoid on, TCC working and no amperage in the circuit. We were ready but not willing to replace the VCM. We then noticed a harness at the rear of the engine lying on the EGR tube. We lifted it up and used a mirror to see if it had burnt through, and it had [Fig 5].

FIG 5

Figure 5

We determined this was the main harness to the transmission and our TCC control wire was in there. We strapped the harness up and away from the EGR tube and went for a drive [FIG 6].

FIG 6

Figure 6

The transmission and the TCC worked flawlessly. Carman then dissected the harness and found our brown wire was burnt and shorting to the EGR tube. [FIG 7]

FIG 7

Figure 7

After a few minutes of thought, the mystery in my mind was solved. There were supposed to be a couple of harness retaining clips that held the harness up off of the EGR tube that were missing/broken that allowed the harness to come in contact with the EGR tube. There was also still enough wire insulation left that when it cooled off the short to ground was not present until the EGR tube got hot enough to melt through the insulation and bring the circuit to ground. So why did the circuit ground, solenoid function, TCC on and no current detected in the circuit? It was my current clamp placement! The circuit was completed at the EGR tube from the fuse instead of the VCM supplying ground. My amp clamp was outside of that circuit, as I had placed the amp clamp very close to the VCM connector C2. The VCM in turn would not ground the circuit because the code had set once the brown wire touched the EGR tube and no longer sensed voltage at the VCM. Had I used a fuse buddy loop and had the amp clamp at the fuse box, I would have seen the amperage when the wire shorted. At that point I could have certainly condemned the VCM for randomly grounding the circuit and I would have been very wrong. Sometimes it’s good to be lucky.

Note: Someone, a.k.a. me, did not zero his amp clamp on some of the scope captures. That is why it looks like it is below 0 amps.

Don’t Be Fooled By The Tool

By Barry Bartlett, Diagnostician

bartlett-barryBarry has over 45 years of automotive experience. He has done everything from managing, owning, and operating his own general repair facility to working in the transmission industry. He’s an ASE Master technician with L1 advanced level diagnostics, the highest level of certification available. Barry and his wife Janet have been married over 40 years and are proud parents of 6 children and 26 grandchildren.

An ASE Quiz (not an official ASE test question)

A 1998 Mustang GT “shifts good” through all gears and has converter lockup, but the speedometer is dropping out after driving a short distance. The scan tool shows that there is a VSS signal and reads correct speed when the speedometer drops out. There was a code in history for the VSS but after clearing it did not return.

Technician A says it is a problem in the instrument cluster because it continues to shift properly, and the VSS signal shows correct speed. Technician B says that the computer may be lying to the scan tool and the signal could actually be dropping out. Who is correct?

(A) Technician A

(B) Technician B

(C) Both technicians are wrong

(D) Both technicians are correct

A customer showed up to one of our retail locations with a very clean 1998 Mustang GT, and the vehicle had no 4th gear, burnt fluid, and a P0734 code. Nothing else on the evaluation had raised any red flags; the car was in really good shape and very well cared for by the owner. The car was 100% stock with no modifications which is really kind of rare for most of the vehicles of this type and age that we see. It was recommended to the customer that we install one of our remanufactured transmissions, based upon our evaluation. The vehicle owner of the vehicle requested that we build the transmission from his car instead of exchange, as he was the second owner and wanted to keep the car “factory”. Honoring his request, we pulled the transmission and sent it to our remanufacturing facility.

We received the unit back completely remanufactured, dyno-tested, and ready to install back into the vehicle. With the transmission installed and road tested everything was working very well and we delivered the Mustang back to the proud owner.

After a couple of months, the customer returned with a complaint that the speedometer would drop out intermittently after it had been driven for a period of time, so I hooked up the Verus Pro scan tool and went for a road test with the car until the speedometer quit working and observed that the VSS continued to show the correct speed on the scan tool. I noted that the transmission did not seem to have any shifting issues while this event occurred.

A look at the wiring diagram showed that this vehicle had both an Output Speed Sensor (OSS) and a Vehicle Speed Sensor (VSS) on the transmission. The wiring diagram also revealed that the OSS circuit connects to the PCM, and the VSS circuit connects to the PCM, speedometer, and cruise control system. A test drive with the cruise control activated at the time that the speedometer was working revealed that the cruise control was inoperative, so that could not help in diagnosing the issue.

The question: was the speedometer bad, or did the speedometer lose signal? If it was the latter, was it the VSS circuit or the VSS itself causing the loss of signal? The instrument cluster was easy to pull out, so a few screws later and the cluster was out and our lab scope was connected to the speedometer signal wire from the VSS. During the second road test I observed that when the speedometer dropped out, the signal that we were monitoring with the scope from the VSS also did so, but the VSS showed correct values on the scan tool with no code set.

Now I was thinking: what would be the easiest way to locate the problem? Could it be a wiring issue or the VSS? If it was the VSS, why did the computer continue to show a correct speed? I then wondered what would happen if I disconnected the VSS and drove it; would it still show correct VSS speed on the scanner? I put the car on a two-post lift and disconnected the VSS. With the VSS disconnected, the correct speed was displayed on the scanner and the transmission shifted through the gears correctly.

Looking at wiring diagrams for later model years of the Mustangs, I noted that the VSS had been eliminated and the PCM was calculating the vehicle speed from the OSS signal, so on this 1998 Mustang it must have been doing the same thing, but not yet eliminated from the system. The only function of the VSS on this application was for the speedometer and the cruise control.

The graph on Figure 1 shows the signal from the VSS and Figure 2 shows the signal from the OSS which the computer is converting for the VSS reading.

FIG 1

Figure 1

FIG 2

Figure 2

After some further diagnosis on the VSS circuit, I determined that it was the sensor itself that was dropping the signal. After the VSS was replaced, the customer had no more issues with the speedometer and we had a happy customer that would recommend us to his friends.

The conclusion: the PCM can sometimes give false information to the scan tool, and therefore is not a foolproof way of diagnosing a vehicle. It cannot be solely relied upon for diagnosis. The scan tool will only point us in a direction to explore and we must investigate thoroughly to find the problem. A DVOM can be used at times while diagnosing, but you cannot see the signal integrity or erratic signals with a DVOM as you can see with a lab scope. A lab scope is a must when it comes to testing computer systems because it lets you see what the computer is seeing as well as how it is controlling electrical components. As it turns out, “Technician B” is the rock star.

Make Use Of All Available Technical Resources

By Daniel Skinner, Diagnostician

Daniel is a Diagnostician for Certified Transmission’s Blue Springs, MO shop.

When diagnosing today’s complex vehicles, we have a wealth of information at our disposal. How we use that information is crucial in making the correct diagnosis the first time, every time. In some cases the diagnosis may be cut and dry (fluid is burnt, the pump is whining, and the vehicle will not move). In other cases, the diagnosis may not be as easy, or worse; we may “think” or “assume” we already know the problem.

One of the most useful, yet easily overlooked pieces of information is the use of TSBs. Unless it is a “cut and dry” diagnosis, referring to TSBs should be routine in your everyday diagnostic practices. I cannot begin to count the number of times this has helped me by pointing me in the right direction, and even kept me from making the wrong diagnosis completely.

A perfect example of this came into the shop recently: The vehicle was a 2007 Toyota Camry with a U660E Transmission. The customer’s complaint was that the car had a 2-3 shift flare when cold. I was able to perform our initial evaluation about an hour after the vehicle was dropped off. When road testing the car, I felt NO 2-3 shift flare. In fact, the transmission seemed to work flawlessly. There were no DTCs and the fluid looked brand new. My next step was to let the car set overnight. Upon driving the car the next morning, the 2-3 flare finally showed itself, but only on the first two 2-3 shift cycles and within a mile the shifts were back to normal.

I continued on with the evaluation by conducting a battery/charging system test, voltage drop test on the ground side of the system, undercar inspection, and a more thorough inspection of the engine compartment, looking at wire harness routing and see if I could tell if any previous work had been performed. I then let the car set outside and cool back off for the rest of the day. Just before close, I took the car out once more and reconfirmed the same symptom of a 2-3 flare on cold startup/driving.

At this point, I am assuming there is an internal mechanical transmission problem occurring. A five minute search of TSBs quickly changed my mind. Toyota TSB TC007-07 describes possible shift flares on 2nd to 3rd and/or 4th to 5th within the first ten minutes of operation.  A TCM reflash is advised by Toyota to resolve the condition.

After updating the TCM calibration through Toyota’s TIS Techstream (fig.1), and performing the shift re-learn procedures, I let the car cold-soak overnight. The next morning’s test drive resulted in perfect shifts. The 2-3 up-shift flare was gone and everything was working well. Just to be safe, I let the car cold-soak two more times, each time the transmission worked flawlessly. Needless to say, the customer was elated when he found out he did not have to replace the transmission.

fig.1

Another good example was on a 2008 GMC Sierra 1500 4×4 with a 4L60E transmission. The customer complaint was “Shudders on the highway while maintaining speed.” While I was test driving the truck, I observed a fairly harsh vibration when the converter was in lockup, and ONLY while maintaining speed. If I accelerated, or decelerated, the vibration disappeared. Upon further investigation, I noticed that the vibration was only occurring during the application of active fuel management (AFM).

When I returned to the shop, I did a quick search of TSBs. Entering the vehicle information in both ALLDATA and Mitchell did not reveal anything that matched the vehicles issue. At this point I could have gone forward diagnosing blindly, but something was telling me to keep looking. I don’t know why, but I just must have had one of those “gut instinct”-type of things going on, so I kept searching, and lo and behold I found what I was looking for: GM bulletin (PIP4371A) regarding harsh TCC vibration in active fuel management V4 mode.

This bulletin states that TCC slip should NOT remain at “0” when applied, but should increase to 20 RPM or greater. If TCC slip remains at zero RPM, this indicates a problem with regulator apply valve (380). A second test drive, while monitoring TCC slip, proved this to be the problem. TCC slip was at zero (fig.2), not allowing a “cushioning” effect to dampen vibrations caused by cylinder deactivation in active fuel management V4 mode. Now this is not technically a “TSB”; it is an unpublished bulletin from GM referred to as “Preliminary Information” that, as far as I know, is only available with a paid subscription to AC Delco TDS Service Information website, but can also be found on Identifix.

fig.2

The customer elected to replace the transmission as advised, and the vibration was no longer present after the unit was replaced. In this case, I was able to pinpoint the exact problem by simply doing a little bit of searching, and using a scan tool.

These are just two examples of how TSBs have assisted me. I adopted using a “TSB search” in my diagnosis routine several years ago. I cannot begin to count the times that it has helped me. In many cases, the manufacturer has done the hard work for us, especially regarding odd problems, or problems we have not yet seen on later model vehicles.

In our business, the saying “time is money” is heard over and over again. Either of the two vehicles I have discussed here could have taken hours of driving, speculating, and even major disassembly just to pinpoint the problem. That is usually a very difficult sell to a customer. In both of these cases I spent no more than thirty minutes searching, finding, and verifying what I was looking for. None of us know all the answers, but there are vast resources for us to access. The correct utilization of the information we have available to us separates us as professionals. It also creates loyal customers who are confident in our professional abilities.

Don’t Ignore The Obvious Issues

By Dan Frazier, Diagnostician

frazier-danDan has been in the automotive industry for over thirty years and is an ASE Certified Master Technician. Dan has a college background in electronics engineering and specializes in diagnostics and computer controls for Certified Transmission.

I’ve always loved cars and knew from an early age, that I wanted to be a mechanic when I grew up. Well, I haven’t grown up, I’m not a mechanic – I’m an automotive technician, and I’ve been fortunate to have able to see the progress of automotive technology over many years. The evolution and integration of computer controlled components and their speed and accuracy has and will continue to change the challenges of diagnosing these systems.

How we go about diagnosing electrical and computer problems all depends on what rolls in the door, but the same basic strategies can be applied to just about anything with 4 wheels and a battery. That being said, you have to take into consideration your resources, capabilities, tooling and experience to know what you can make a profit on.

The 1st step is just doing an initial evaluation on the vehicle. Does it start, run, or move? Everybody does this differently but needs to include at a minimum a fluid level check, a visual inspection, and a test drive with a scan tool. I like to take movies of the scan data in case I need to go back and look at anything – volumetric efficiency come to mind.

OK, you got paid for your first .5 for your professional opinion of what is wrong with this transmission. So what else do we need to know? Won’t move, full of burnt fluid at 175k, needs a unit, I’m OK and move on. Need to do pressure tests or electrical evaluations? That’s different. Got a 08 BMW 550i that intermittently has the transmission go into limp mode and has low voltage and communication codes in just about every module? To the dealer it goes – with the aftermarket wet-cell battery that wasn’t registered to the vehicle. Got a 2000 Dodge Ram 5.9 gas with a P0753 – 3-4 shift solenoid circuit? I’m all in. How about a 2006 Cobalt with TCM communication issues intermittently that comes from another very good shop that wants a second opinion? I’ll swing a bat at that because I’ve got plenty of resources to help me deal with issues like that.

So what are your resources? O.E. and aftermarket scan tools, service information from various providers, information from professional trade groups, and personal experience in the field to name a few. I have access to some O.E. Scan tools and reprogramming, but BMW isn’t one of them. I also have your standard service information providers, and it seems a lot of information is very limited on Euro stuff. I have a lot of experience in electrical diagnostics, but again, very weak on Euro and very strong on domestic car lines. That’s why the BMW left and the old Dodge truck and Cobalt stayed.  Everyone has strong and weak points – take advantage of your strengths and try to learn more on your weaknesses.

So let’s talk about this fine 2000 Dodge Ram with the P0753 – 3-4 shift solenoid circuit, after seeing this on my initial inspection.

Figure 1

Figure 1

I recommended 2 hours of diagnostic time. I’m pretty used to seeing bungled up wiring, usually caused by rodent damage or bad installs, but wasn’t sure where this diagnosis would lead me. I knew how to fix the duct tape on the TV cable though. The code was set for a specific circuit and I had a good idea where I would need to go with this. One of the 1st things I considered was this was a circuit code as opposed to a performance code.

If I have a circuit code, the controlling device has detected an electrical issue, like a short or open, rather than a failure to respond to a command. Failing to respond to a command would usually result in a performance code. The module in control doesn’t see the expected results from the command but sees no issues electrically. The computer can be applying a clutch pack, VVT solenoid, fuel injector, or whatever – and it knows what changes it wants to see under certain conditions. This will help to lead you in what direction to go. If I have a circuit code, I’m busting out the electrical diagnostic stuff. If I have a performance code, I may be checking pressures or other data on the movie I took while on my initial test drive.

OK, I’ll spill the beans early; it’s another Chrysler with a bad PCM. After seeing the multiple butt connectors on the injectors, I was really thinking wiring damage was part of the problem, but I went after what the PCM was seeing to set this code.  The PCM is seeing the wrong voltage on the 3-4 shift solenoid circuit when it’s commanding the solenoid on or off. On this particular transmission, electrical diagnosis is fairly easy, as there only a few electronically controlled devices – the pressure control solenoid, TCC solenoid and the 3-4 shift solenoid.

Figure 2

Figure 2

We can see B+ supplied to the transmission from the Transmission control relay to the solenoid pack at pin 1. If I had an issue with the power supply to the solenoid pack, I likely would have seen codes for the other solenoid circuits or transmission relay stuck on or off. Ground for each circuit is provided by the PCM. So I can easily check total circuit resistance by removing the transmission control relay, and measuring the resistance between pin 87 of the relay and the control pin at the PCM. I had 28 ohms; spec for this circuit is 20 to 40 ohms, so I felt I was good there. Easily from there, I can check for a short to ground (which there wasn’t), or to power. Now, with the transmission being in limp mode, it shuts off power to the transmission control relay, so you will have to supply power to that circuit by activating the relay with a scan tool, or by using a fused jumper wire or relay bypass and check voltage at the PCM control wire. With power supplied to the circuit, I had close to no voltage at the PCM control wire when the solenoid was commanded off, where I should have close to B+. Unplugging the connector to the PCM gave me a reading of battery voltage at the PCM connector, proving the PCM had an internal short on the 3-4 shift solenoid circuit. A used PCM and a TV cable (remember the duct tape?) and this one is out the door.

BTW, the story behind this particular vehicle is a comedy of errors so to speak. A young kid bought this truck knowing it had a transmission problem – stuck in limp mode. Took it to 2 different shops and was told it needed a solenoid, or some other misinformation that I don’t know. Bought a new transmission, installed it and had the same problem as before. It took less than a half hour to reach the correct conclusion as to what was wrong with it.

Ok, we made a little bit of money on that diagnosis. What about this 06 Cobalt with intermittent TCM communication issues? We’re going to fix this one by using a kind of different approach. Resources and experience is going to be the key on this one.

We had a very good wholesale customer wanting us to take a look at this Cobalt that intermittently (several times a week) the transmission would go into limp mode and then be OK after the key was turned off and restarted. The shop had already replaced the TCM and flashed it to the latest calibration.

I’m a big fan of the IATN website, (International Automotive Technicians Network), and have used it’s database, waveform library, and forums to expand my knowledge and help me gather information about a lot of issues I can use in my everyday routine. If you have Identifix, there’s a link to IATN on the home page. Some time ago, I had come across a discussion in the Technical Discussion Forum about the use and issues that aftermarket devices such as insurance dongles, remote start systems, etc., can have an effect on communications, driveability, and transmission operation on GM vehicles. It gives a pretty detailed list of codes and symptoms that can be caused by such devices. If you want to view it, it’s in GM Tech Connect from Feb 11, 2013.

Anytime I get a vehicle in with communication issues relating to the transmission, one of the 1st things I look for are any added switches, LED’s, or anything that would indicate a non-O.E. device being installed. Another good thing is to take a quick peek under the trim panel below the steering column. If you find something like this, you might want to remove it and see if your issue goes away.

Figure 3

Figure 3

On this Cobalt, I found a wire tapped into the hi-speed CAN circuit that was intermittently causing a communication error. This picture isn’t from the Cobalt (clutch pedal?) but gives you an idea of what to look for. And while you’re looking, be especially wary of those dang Scotch-locks that seem to be so popular. Once you cut into a wire, the damage is done and it can be very difficult to trace a wiring issue down after the fact.

Expanding your knowledge base and resources is often crucial to your success and sometimes doesn’t cost very little if anything at all. Talking with other shops, technicians, networking with other professionals through electronic media, and sharing with others is almost necessary today to keep at the top of the pack.

Undesirable Effects of Dodge RAM Front Suspension Modification

By Larry (LJ) Porter, Diagnostician

porter-ljLJ has worked for Certified Transmission for over 20 years and is an ASE-certified technician in transmissions, transaxles, manual transmissions, steering, suspension and brakes. He was a remove and replace (R&R) technician for 6 years and has been a diagnostician since 1996.

One of our regular customers brought in their 2006 Dodge Ram 1500 4WD with a 5.7L engine mated to a 545RFE transmission. The owner’s concern was a very bad shake when accelerating while having the 4WD engaged.

I proceeded with an evaluation of the issue. We have detailed procedures for this process, including but not limited to a battery/charging system analysis, complete module scan for DTCs, road test, visual inspection, and TSB search. During the road test I was able to duplicate the customers concern. On acceleration in 4WD, the truck had a pronounced wobble, or shake. When the truck was driven in 2WD the concern was not there, eliminating some of the possible causes for this issue. The under-car inspection did not reveal anything that I would consider abnormal for the age and mileage of the truck. The fluids in the transmission, transfer case and both differentials were in good condition, but the front differential was a bit low due to a small axle seal leak. However, no clues as to what could be causing the issue.

There was some evidence that someone had worked on the front differential previously, or at least had removed an axle. The customer has had several other vehicles into our shop before and we had a good relationship with him so I had the manager call him and see if there had been any other work done, especially to find out if anyone had tried to repair the truck for the shaking problem before it came to us. From that phone call we learned that the truck was purchased at auction about 30 days prior to the shop visit, and therefore had no known previous repair history.

After the customer consented to some diagnostic time, I decided to start with the easiest thing I could do and removed the front driveshaft. Both the single front U-joint and the double cardan joint felt fine with no binding or play in either of them, so I left the shaft out and went for another road test. With the front driveshaft removed the wobble was gone, even in 4WD. I fully expected this since there was no load on the 4WD components.

Once back in the shop, the truck was placed onto a two-post lift so the front end components could be examined with the suspension unloaded. I will start with saying that this truck was not in perfect condition, and while inspecting the front end components there was a little bit of play in the tie rods and the pitman arm. While not very bad, it was still something that I could not rule out 100% at this point. I checked the tire circumference with a stagger gauge and it checked okay. Prior to removal of the front driveshaft, I had also driven the vehicle in a straight line while in 4WD with no evidence of any type of binding concern, so I knew that I wasn’t dealing with a gear ratio difference between front and rear differentials.

Getting back to the wobble, I can best describe what I felt as similar to a shake or vibration caused by loose front inner CV axles in a front wheel drive vehicle; when the inner CV joints get loose it can cause side to side type of sensation that we usually refer to as a “wobble”. This truck felt very similar to that, but since this is a 4WD vehicle and power is supplied to both front and rear, there is just enough difference in the feel that I was hesitant to condemn the CV axles as the culprit. While there were a bit of play in both of the inner CV joints, it didn’t seem to be enough to be the cause.

I sent an email to some other diagnosticians within our company to see if someone had dealt with a similar situation. The responses I received targeted either front-end steering components, or a bad axle. While I was waiting for response from my fellow associates, I rotated the tires front to back to see if I could “move” the sensation but yet again was unsuccessful in pinpointing the cause.

Since I could feel some play in the inner CV joints, I decided to replace both of them with reman axles from one of our parts suppliers. Yes, you guessed it…the wobble was still there. I don’t think it changed even a little bit. Disappointed but undaunted, we reinstalled the customer’s original axles back into the truck and continued the diagnosis.

Fortunately around this time we had another 2006 Dodge come into the shop, but this one drove fine in 4WD with no signs of a wobble or vibration like the problem truck had. At least now I had something to compare our subject vehicle to. We only have one drive-on lift available in the shop, so it was hard to do a side by side comparison of the two vehicles. Nonetheless, I still could not really see a difference in the CV axle angles or driveshaft angles between the two trucks, but I was still convinced there had to be something I was missing. Since there was some play in the pitman arm and tie rods we replaced those parts and had the truck aligned at a nearby general repair facility, but yet again did not fix the problem.

When I returned to the shop I parked the truck in the back lot alongside the other 2006 Ram and went in to speak with the manager to tell him the news. I am really frustrated at this point because I am having difficulty fixing this truck. When I go to the back lot to test drive another vehicle I look at my nemesis sitting there and I noticed something: the front end of the problem truck is sitting a couple inches higher in the front as compared to the truck that does not have the issue. Neither of these trucks has a lift kit installed, but both have stock-sized tires; so why is the ride height different?

I took a closer look at the front springs and noticed that there was more space between the spring and the upper spring perch on the subject truck than on the comparison truck.

I do a little research and find that there are companies selling a “leveling” kit for these trucks that is just simply a block to increase the installed spring height intended to raise the front end ride height, but without addressing the increased front CV shaft angle.

Now, to answer the question: why does this have such a big effect on the way the truck drives when it only adds a couple of inches to the ride height? The differential is attached directly to the motor mounts and moves with the engine. Because of this, the differential rotates upward on the passenger side when the engine’s torsional forces are active upon acceleration. This, combined with the increased CV angle from the spacers (without a differential drop), causes the CV joints to bind under a load.

We removed the “leveling” kit which should be renamed to, “Change your driveline angle kit”. Predictably, the wobble was gone and the truck drove like new again; well maybe not new, but you know what I mean. It’s worth mentioning that there are other brands of leveling kits available that will raise the front end of the truck the correct way to get rid of the factory rake these trucks are built with, yet do not change the driveline angle. These kits are more $ than the $50.00 – $100.00 kits, but the results would be well worth it. This is just another example of how aftermarket parts can deal us fits!