If you can drive the car.
Get it going 25 MPH, shut off the engine, in 5th gear with the clutch disengaged (pedal to the floor).
Downshift progressively to 1 st gear as you coast down from 25 MPH.
With the engine off the flywheel is stationary, the clutch disc is spinning between the flywheel and clutch pressure plate. Any flywheel problem will not exist with the flywheel stationary.
As you downshift the imput shaft bearing noise (assuming it has one) will get progressively worse.
Next put it in neutral with the engine running and put your ear on the shifter. Depress the clutch and see if the noise goes away. This is another indication of a bad imput shaft bearing. If you only hear it depressed then it is a bad throwout bearing.
While the coincidence of two different transmissions having the same problem is unusual, a typical problem like bad imput shaft bearings would definitely mean there could be two trannys with exactly the same problem.
Thats why they were removed and sold by unscrupulous people. We had an attic full of transmissions with bad imput shaft bearings we used for parts, but they were for Nissan Z cars (used to be Datsun). Typically they all neeeded that bearing by 150 k miles.
If you go into the tranny replace all of the bearings, or put wing nuts on it so you can get it out faster on the repeat R&Rs. We always had people who questioned our procedure, thinking we only needed to replace one bearing. I told them they could specify we only replace one, but they could potentially end up pulling the tranny 6 times at $150 a pop.
Last edited by user removed; 10-20-2012 at 10:02 AM..