Spun bearing or loose flex plate???

[89blkvet]

My 89 started to make this slight knocking/vibrating type sound from under the car somewhere. I have taken it to 2 different mechanics and one said it could be a loose flex plate, the other said it could be a spun bearing. The car has 75000 miles. has anyone ever experienced this type of situation, and if so what was the outcome? How can I be sure which of the problems mentioned above is actually the one I should address??

 

[evolution]

My bet is loose flex plate. Those bolts can come loose and it makes for a weird noise that is syncronous with RPMs.

Jack it up, take off the flexplate shroud, get a large screwdriver or prefferably a pry bar and tighten those up. The prybar btw is to turn the wheel around.

 

[jmccloud]

Flex Plate

I've seen two flex plate 'failures'
The first sounded just like a spun bearing except the noise was loudest at no load rather that high load. When we dropped the trans, there was a crack in the plate, nice and shiney where the two surfaces had been popping back and forth across each other.
The second was strange; sounded almost like popcorn popping at idle but only an occasional crash at speed. Dropped the inspection cover and two plate-to-converter bolts fell out (less than 5000 miles).
Take the cover off and make sure the bolts are tight, looking for cracks anywhere in the plate.
Good luck