Converter rebuilders have been challenged with torque converter pilot wear for years. A worn pilot can cause all kinds of problems if not addressed: Vibrations, leaks out of the front of the transmission, irregular noises, and cracked flywheels are just a few.
Torque converter wear seems more prominent on the heavier converters. For example, it’s not uncommon for pilots on the 4L80Es to develop considerable wear. Converter rebuilders have often welded worn pilots and machined them back to the original size. This is a common repair method, but one thing that we don’t always pay attention to is the mating hardware or part.
This can be a spacer, a bushing, or the actual crankshaft of the engine. While it’s common to replace a spacer or bushing as needed, it becomes a greater challenge to identify and resolve extensive crankshaft wear. Since we can’t replace the engine for a transmission job, shop owners or managers must educate the R&R technicians to be aware of the problems in these areas. Correcting the issue during a rebuild will save more time and expense later on.
Upon further inspection, we discovered a worn crankshaft and torque converter pilot (figures 1 and 2). The image indicates a mark in the back of the crank. This mark is actually a deep groove from the torque converter pilot. Not only is the crank worn, but the torque converter pilot is also worn.
We’ve seen this problem within the past six months, when the same type of vehicle came in with a leak that developed in front of the transaxle. It had also been previously repaired and failed.
We also repaired and modified the pilot in both vehicles (figure 3). This repair straddled the wear in the crankshaft, and most of the time you won’t be able to make a repair as extensive as the modified pilot.
- Rotate the crank to align the worn part of the crank at the top.
- Continue installing the transmission.
- When you’re ready to install the torque converter bolts, install and mark the first bolt.
- Rotate the crankshaft and install all of the other torque converter bolts.
- Tighten the marked bolt.
- Rotate and tighten all the remaining converter bolts.
This allows the weight of the converter to rest downward on the unworn part of the crankshaft, which will align the converter more closely to the centerline without rebuilding the engine.