[Danglerb]

Symptoms fit, and thrust bearing failure wrecks the whole motor if not caught very early.

On later model automatic transmission 928's the engine flywheel has a flexplate bolted to it and the torque tube shaft is connected to the flexplate with a pinch clamp. Normally the flexplate provides all the compliance needed for front to back movement, but sometimes the pinch clamp slips, and unfortunately is seems to only slip in the forward direction eventually applying a lot of pressure to the flexplate and from that directly to the crankshaft. The thrust bearing simply is not designed to bear that kind of load for long periods and quickly wears through and WHAM crank meets block. Bits of bearing are all through the motor by then, and damage is often enough that the whole motor must be replaced.

Recommended service is to once or twice a year check the flexplate for flatness and release the tension measuring how much the pinch clamp moves, then checking the endplay of the crank.