[11echo]

BOY I HATE Vibration problems!!! I DON'T think "shoulder bolts is your problem. ANY 3/8" bolt will have same dia. of 0.375" so having a shoulder won't do anything. BUT you have to have a GOOD grade bolt ...say GR. 5 minium or GR. 8! But this again is not your problem. I'm guessing the main input shaft bearing is bad! On rebuilds alot of the time guys clean up the parts and use the ones that don't look bad. The main input bearing can "look" good but still be bad. I use to check mine by using compressed air to drive the thing up to speed, and if they were bad a harmonic vibration would set in (damn things would almost take your fingers off!). Sometime "cheap new bearings" would do the same thing. I would go back to the trans re-builder and talk with him. Ask him how he did yourr trans. My 2 cents ...Good Luck! ...Mark