I finally pulled the transmission and bell housing on my 85 IROC to swap in a GM light-weight flywheel and Center Force clutch kit only to find that the inside of the bell housing, the back side of the flywheel and the clutch disc were pretty much oiled up--which was the probable cause of the groan I was hearing (I figured TOB or pilot bearing). Is there any way to determine if the cause is from the rear seal or the oil pan (the bolts, especially the rear ones, were a quarter turn loose)? By the way, the underside of the car showed definite signs of blowing oil.

JamesC

 

I think you got it right, problably both. The inside of the bell housing being wet is a sure sign the rear main is leaking and the loose bolts will only add to the problem. I've experienced both conditions though my car is an automatic, my dust cover was wet on the inside as well as the oil pan bolts being loose. I had the typical bad rear seal. Good time to change it since you have the trans out. Good luck..