I just discovered what was has been causing a hard to find noise that occurred around 2K rpm on my 89 745T automatic. See http://brickboard.com/RWD/index.htm?id=713863 for background. Disconnected torque converter started engine, noise still present(not trans). Examined flywheel for cracks (none). Then reconnected torque converter with inspection cover/trans bracket still off, started engine, crawled underneath. Could hear very close by, but hard to pinpoint source. With a hose I found the source to be the starter gear. It is ever so slighty being clipped by the flywheel teeth as the crank flexes? under power. With the car off,the starter gear is only about 5-10 thousands from the flywheel. My mechanic advised me it should be a considerable amount away. When the car is started the gear isn't returning far enough away. So I will replace the starter assy. Apparently this has been going on for a while, as about a 60 thousands has been worn from the stater teeth. The noise has been masked by very noisy alternator bearings, which were fixed to weeks ago.
I noticed when under the car with the engine running that the flywheel is not perfectly flat. I know on a stick shift car a flat flywheel is critical, but how much is deviation is OK on an automatic? Is there a spec for this? Thanks.