For those of us that have spent a fair amount of time in a shop, you have to wonder if there would ever be a time when you could say, "I've seen it all.. It seems that every day we run into some variation of a problem that is just unique enough that we have to start diagnosing from a clean sheet of paper. While this scenario involved a mechanical issue, it was, well...different. Somehow these kinds of stories often seem to involve a previous repair performed by another shop, and this story is no different.
The vehicle was a 1995 Ford Ranger 2WD, equipped with a 4R44E transmission. It had originally been repaired by a local transmission shop that had R&R'd the unit and rebuilt it in-house, though we had no knowledge of what the original complaint was at the time. After their repair, it would set a P0741 (TCC stuck off), OD light flashing, etc. They'd had the vehicle for quite some time, but then decided to purchase a remanufactured unit from one of our distributors when repairing the rebuilt unit was unsuccessful. After installing the remanufactured unit, the same code and symptoms returned. It was then that the vehicle was brought to our shop for diagnosis.
After verifying the concern and pulling codes, I did some basic tests to determine if the PCM was commanding the TCC solenoid correctly, and to make sure the TCC solenoid was functioning properly. I found no problems with the solenoid, circuit, or PCM command. While watching the TCC slip in the PID data while driving, you could see the TCC start to slip and as soon as it hit 200 rpm, the OD light began to flash. With this solid information I made the determination that it had to be an internal problem with the transmission. I would later discover that I was right. Well, sort of.
We ordered a replacement unit from our plant. As we're completing the unit installation, my R&R tech discovers a couple of extra washers lying on the frame rail. We looked at all the bolts and couldn't find anything missing, so we buttoned up the vehicle and proceeded to start the engine.
Upon startup, my ears were treated to the familiar and troublesome "screech" of a starter drive still engaged. I looked up through the inspection cover and the starter drive was hitting the flexplate. That's when the R&R tech said that, during the installation, it seemed like the converter had to pull away from the transmission much farther than usual in order to mate up with the flexplate. That's when the red flags began to show themselves. Now we had something to look at.
We pulled the starter out to make sure that the drive gear wasn't seized or sticking, and it wasn't. After some pondering and a closer look, we determined that the extra washers were being used as starter shims between the starter & transmission. Those of you that know Fords also know that they don't use starter shims from the factory at all.
What we think happened was the first R&R tech didn't have the converter studs lined up when he mated the in-house rebuild to the engine, zipped the bellhousing bolts down with his 1/2? impact wrench, and inadvertently bent the flexplate in. This caused the sealing ring for the TCC oil supply to barely seal on the torque converter (because of the converter was being pulled an excessive distance away from the transmission), and letting the TCC lose pressure. That also explained why none of the other units functioned properly, either.
We ordered a new flexplate for the vehicle, and when the new part was compared to the flexplate that we had removed from the vehicle, we found that it was almost 1/2? taller. After the installation was completed with the new flexplate, we performed a few road tests to ensure that the issues were completely resolved. No lights came on during the road tests, and no codes were set. The vehicle was released to a smiling customer.
We'll never know exactly what caused the bent flexplate in the first place, as it is possible that an incorrect, used flexplate was installed due to ring gear wear. Or the original tech simply made an installation error. Who knows. It just goes to show that anyone can make mistakes, and some of them are just harder to find than others. The phantom washers were the giveaway in our situation, but sometimes the clues aren't so obvious. Just when you've thought you've seen it all, know that you never will, at least not in the repair business.