95 Jeep Grand Cherokee 4.0 2wd

alvinscan

I was having tranny issues. I pulled the tranny and the shaft is chewed. I know I have to replace the torque convertor and the drive plate. What would cause this shatf to get all chewed up? Should I look further into the engine?

93tracker5spd

Hello! Since you state "torque converter", I know you have an automatic transmission. When you say shaft, I assume it to mean the power input shaft (at the front of the transmission). To help you better understand what you are looking at, this is how an automatic transmission works. It uses the torque converter as a replacement for the clutch you would have in a vehicle with a manual transmission. Two impeller turbines are housed in that converter along with some of the transmission fluid. One turbine is mounted so that it can rotate freely inside the converter housing, since the housing is bolted to the fly-wheel which is bolted to the engine output shaft, the converter spins all the time the engine is running. When you accelerate the engine turns faster, thereby turning the converter faster, this pushes the fluid inside the converter around and around. As the fluid gos around faster it builds pressure against the other turbine, this makes the other turbine spin as well. Now the part that applies to your question: That power input shaft, the one that is all chewed up, has splines on it that fit into splines inside the hole in the center of the torque converter, these splines are machined into the other turbine, the one that only turns when the converter spines faster. Three things can chew up these spines:

1.) If your transmission locks at a relatively high speed stopping the input shaft from turning with the torque converter, this can destroy both the splines on the input shaft and the splines inside the converter.

2.) If the torque converter fails and locks up, it can destroy both the splines on the input shaft and the splines inside the converter.

3) If someone recently changed the transmission, and the input shaft splines were not lined up correctly with the splines inside the housing, or the transmission pump engagement wasn't aligned correctly upon installation.