Harmonic Vibration

[KillerKittyCat]

My 65 "A" block 4 speed has developed a driveline vibration which occurs over 2500 RPM. I was having tranny problems and found out that the tranny had loosened from the bell housing. Tightened everything down, Rear main is leaking. The vibration is ongoing coming every two to three seconds. Not bad but just enough to twist my brain.
Crank???
Bearings??
Tranny??

I need ideas!!

 

[wild70stang]

Dozens of people say its the yokes in the drive shaft that are worn can cause a really pain in the @$$ vibration which could cause ur bolts to come loose.

 

[KillerKittyCat]

Driveshaft and tail shaft appear solid. I hit 70 with the vibration and push in the clutch the vibration goes away after the RPM's come down. I'm thinking crank or pilot bearing.

 

[SoCalCruising]

Does it vibrate when accelerating, only; or decellerating, only; or at all times when the clutch is engaged? Is it tied to engine RPMs? Or just wheel RPMs?

 

[66candy]

Try a new transmission mount!

 

[KillerKittyCat]

The vibes are engine RPM related through the tranny. Engine will rev just fine. Thinking it is the pilot bushing and\or input shaft bearing. I just do not have time to pull it right now.