It’s the little things: Double-checking and doing the basics in transmission repair - Transmission Digest

It’s the little things: Double-checking and doing the basics in transmission repair

As transmission technicians, problem-solving is what we do. We see that box that says “customer states” and we already have an idea of what is wrong, and 99% of the time we’re right. After all, it’s the eighth 6L80 we have seen this month. But with an endless list of components and ever-evolving technologies it can be easy to miss the mark, especially when we get comfortable or run into an issue that we have never seen before.

It is not uncommon to encounter a symptom or a condition that you know is remedied with this repair. One example I encountered was a 2007 Tahoe 4×4 with a 5.3L engine and a 4L60E transmission.

The customer stated that there was a whining/grinding noise behind the driver’s seat when accelerating or decelerating, and that the noise was worse when the vehicle had warmed up or been driven a few miles. It had already been to another shop and diagnosed with a rear differential problem, and their recommendation was to replace the axle with a remanufactured assembly, so they installed a replacement unit.

The vehicle had oversized wheels and tires that were not quiet, and on the initial test drive there was a loud grinding noise in the rear that was worse when accelerating and decelerating. It sounded like an open and shut rear differential pinion bearing noise. The vehicle had a suspension lift. When I checked it, there was no discernible play in the pinion bearing. The vehicle was run on the lift and a stethoscope used on the differential housing. A loud grinding noise was heard there, so a recommendation was written up for a rear differential rebuild.

After I checked out a few more vehicles, I was still thinking about this Tahoe. Some things weren’t adding up. I did not know who the other shop was or where the differential was sourced from, nor the shop’s abilities. After all since it had just been replaced, why did the customer not go back to the shop that just did the work? Did I miss something?

Read more stories in our R&R Tech series here.

I pulled the paperwork back from the service advisor and told him I was going to take a second look at this one. I brought the Tahoe back into the shop and put it on the lift again. I had another tech ride up in vehicle so I could listen from below. Standing under truck, the noise was still the loudest at the rear of the vehicle just like it sounded when driving it. As I start moving the stethoscope around to different parts of the vehicle, I discovered that the noise was loudest at the back of the transmission.

Wow, I almost sold this guy a differential when it was not the issue he came in for. It turned out that the rear planetary was the component that had failed.

We recommended a remanufactured transmission, sold the work and installed our unit. The noise was gone. There were still questions I had, like whether this was the entire problem all along, or if this truck just had two components fail at almost the same time. Still, I am just glad I questioned myself and double-checked my work.

Sometimes a vehicle comes in that has you flustered or overconfident, and you skip the most basic steps that would have stopped you from wasting your time and costing you (and potentially, the customer) money. The following example illustrates this.

A remanufactured transmission was installed in a 2012 Volvo XC70 3.2 FWD with a TF-80SC transmission. About 5,000 miles and two months later it came back to the shop with a complaint of slamming into gear, harsh shifts and a check engine light. The vehicle performed normally on the ten-mile test drive of mixed city and highway driving. Codes were pulled and there were circuit codes for numerous solenoids, any of which could cause hard shifts or cause the vehicle to go into limp mode.

Setting up to test the transmission electrical circuits, I found the A/C compressor and serpentine belt mounted directly above the transmission, directly in the path of the area I needed to access. As if that wasn’t annoying enough, the transmission control module (TCM) on this vehicle plugs directly onto the case connector pass-through, and there is no way to “live” test solenoids or the harness without removing the front cover to access the supply/control sides of the PWM solenoids. That is a lot of work to test the solenoids, but no matter; I get to work. (Seen in Figures 1 and 2).

RR-Tech-August-Figure-1
Figure 1.
RR-Tech-August-Figure-2
Figure 2.

After a few hours I had tested the solenoids and connected the scope. Using the functional tests on the scan tool to operate each solenoid individually, I was looking for any odd pattern or intermittent dropouts and nothing showed up. Puzzled and annoyed, I stepped back and got back to the basics. I tested the battery, double-checked the installation, then performed a voltage-drop test on the grounds. All checked out and were cleared.

Next, I removed the TCM from the case and inspected the pins. There was no corrosion, and the pin fitment was tight. The TCM was re-installed, and that’s when I noticed that the vehicle harness side connector of the TCM did not click in nicely. I scoped the power and ground circuits to the TCM and found that when wiggling the connector, the power dropped out intermittently (Figure 3).

RR-Tech-August-Figure-3
Figure 3.

The little nub that connector clips onto to secure it had been damaged from age and being previously removed, and no longer maintained a secure connection to the harness connector. This was causing an intermittent loss of power to the TCM and putting the vehicle into limp mode. Five hours into diagnosis with a fair amount of embarrassment, I secured the connection and confirmed the repair on a test drive. After confirming the repair, I was able to get the vehicle back to the customer, now happy that their vehicle was functioning properly once again (Figure 4).

RR-Tech-August-Figure-4
Figure 4.

If handled improperly, these situations will hurt your pride and cost you time and money. It is a miserable feeling, but it won’t break you and you’ve potentially learned some valuable lessons. That is why it is important to stop, slow down and do the job right. No one wants egg on their face, and no one wants to waste time, lose money or upset a customer who has spent their hard-earned money putting their trust in you. Follow the process and don’t overlook the simple things. Get the job done right.

About the author: Zack Harkins is a diagnostician with Certified Transmission.

You May Also Like

The importance of the follow-up road test after transmission replacement

A 2002 Lexus RX300 equipped with a 3.0-liter V6 engine and U140F transmission was brought into our facility with a few concerns. The customer said that “it has a leak, a grinding noise when taking off from a stop, and it just doesn’t seem to shift right.” They went on to tell us that this

RR Tech Feature Oct

A 2002 Lexus RX300 equipped with a 3.0-liter V6 engine and U140F transmission was brought into our facility with a few concerns. The customer said that “it has a leak, a grinding noise when taking off from a stop, and it just doesn’t seem to shift right.”

Dealing with the increasingly common pin-fit problem

I want to talk a little bit about a common diagnostic misstep or overlooked problem that is prevalent in the automotive repair industry and seems to be on the rise. Pin-fit or tension can deal us a fit sometimes (pun intended), especially if we do not have the proper tools to determine if this mode

RR-Tech-September-FIG-1-1400
Watch: Replacing a transmission and components

Dave Hritsko and the team have already removed a full transmission in a previous video. This time, see an in-depth explanation of the parts, components, and steps in how they make the upgrade with a remanufactured transmission along with new aftermarket components with the help of students from Ohio Technical College. Related Articles – Cal

Removing-a-Transmission-with-Dave-from-Transtar-1400
Watch: How to remove a transmission

Watch Dave Hritsko from Transtar and team members from Ohio Technical College as they remove an old transmission and replace it with a newly remanufactured transmission. Related Articles – Road to AAPEX season 2 finale: Where the road ends and the show begins – Road to AAPEX season 2, ep. 9: The roads that connect us

Back to square one: When a transmission replacement doesn’t fix the problem

The subject of this article is a 2002 Ford Ranger with a 3.0L V6 engine and 5R44E transmission. There were 191,622 miles on the vehicle when it arrived at our shop. The owner said that the transmission was not shifting correctly and the OD lamp was flashing. Related Articles – Watch out for high pressure

RRfeature-1400

Other Posts

The technician’s duty to the customer

I want to talk about some of the recent trends of particular cars and trucks that we see showing up at repair shops for work to be done. It seems to be a perfect storm of high used car prices, lack of new car inventory, and a bit of economic uncertainty that brings us to

rr-feature-1400
Diving into electrical testing and wiring with the 948TE

We had a 2014 Jeep Cherokee come into our Bellevue, Neb. facility with a transmission that would not shift. This all-wheel drive vehicle was equipped with a 3.2L engine and a 948TE nine-speed transmission. Related Articles – 2024 State of the Powertrain Industry – Powertrain industry directory and buyer’s guide 2024 – Shift Pointers: A

RR-Tech-June-FIG-1-1400
Potential causes of an overheated transmission: It’s not always what you think

If a transmission starts overheating, the root cause must be something to do with the transmission itself, right? Not always. The following are a few examples where the transmission was not to blame. Related Articles – Shift of the shaft: Diagnosing Chrysler 48RE manual shaft issues – Sometimes, a diagnostic code is all you need

A mysterious shudder: Locating a problem with no fault codes

It was a dark stormy night… well, not really; it was just an ordinary Tuesday. Related Articles – Top 20 Tools and Products: The Winners – Performance supplier listings 2024 – Shift Pointers: What to do when the 62TE TRS tab breaks On that ordinary Tuesday, a customer came into our store very distraught. He

RRfeature-April-23