Tailshaft bushing has .018 clearance checked with a dial indicator. Problem is only in 5th gear so believe it is inside the transmission with the overdrive gears.

With the bushing being good, I would suspect a mainshaft that is out of spec.  The 5th gear combo is the closest gearset to where most of them bend.

Last edited by Glens 1965 50 (8/10/2015 7:33 PM)

Tremec indicates .007 but I have seen T5 go as high as .010  Lots of other factors here also. The end play should be at .000 from my personal expierence.  On both the mainshaft and cluster gear.
 

OK, I got the transmission back together and went for a test run last night, the vibration seems to be gone finally, I talked to Paul at the link that BobE posted and ordered the countershaft bearing stabilizer plate to better control the preload on the countershaft bearings, I did recheck how loose the countershaft was and it was .022 where it is supposed to be preloaded 2 -4 inch ponds of rolling torque,  the stamped steel bearing retainer was badly deformed causing this problem, So hopefully this problem is behind me now. 

Another vibration issue I had and found previouly was with the Center Force Dual Friction clutch, the fly weights on the diaphragm fingers were not staying centered under high RPM's because of the heavy ring around the weights the whole assy would move off center and vibrate like crazy, removing the weights resolved that problem, the next clutch will not be a Center Force but will cross that bridge when the time comes.