I have also had the rear thrust plate failure where the rear main shaft bearing started to ream out the thrust plate. The first sign of the failure was a fore and aft movement of the shift lever on acceleration/deaccelation. The next result was slipping out of gear. If someone else has worked on the transmission, it is wise to check the three 1-2 and 3-4 shift rods detent ball/spring/plug preload. It is not mentioned in some editions of the FSM. The correct depth from the top of the plug to the case is .22-.24 in. The small end of the spring goes next to the ball and sealer is applied over each plug. This does not apply to the neutral detent.