Drivetrain vibration - need expert advise on 727 car

[Lifsgrt]

I have a vibration in the drivetrain I and hope someone can help determine what is causing it.  1969 440, 727, and 8 3/4 rear.  Here's the problem- with either 4.86 or 3.23 gears, when engine is nearing max rpm  in high gear, a vibration begins and gets worse with rpm.  It feels like a shaft wobbling inside a bushing that's worn out (best way I can describe it).  Anyone dealt with this before?  Driveshaft is still balanced from the factory and is not bent as far as I know.  Tires are balanced.  Thanks for your help in advance.

[Plumcrazy]

I would check the driveshaft u-joint angles.  On a street car the driveshaft should angle down about 2-4 degrees at the front, while the driveshaft should angle upwards an equal amount at the rear.

[skip68]

Tranny mount?

[firefighter3931]

The tailshaft bushing might be worn out. If there is play in the front yoke then you will experience vibration.



Ron

[Just 6T9 CHGR]

The tailshaft bushing might be worn out. If there is play in the front yoke then you will experience vibration.



Ron

   Im chasing a cyclic vibration that comes in at around 62 mph and smooths out over 70 mph or so.

Recently I changed my driveshaft slip yoke because I felt the play in that area was excessive.  The new yoke tightned up the play a bit but there still seems to be more than "what should be"   Im thinking the tailshaft bushing will be the next to be changed...

[Lifsgrt]

Thanks guys.  Tranny mount is polyurethane and new...u-joints are new also, but had same problem with old ones...pinion/u-joint angles are stock but I haven't measured...I was thinking tailshaft bushing as well, so I'll try that.  Thanks for the help.

[Charger-Bodie]

i would try changing the tranny mount back to a stock rubber one cause them poly ones can multiply vibs.

[RallyeMike]

i would try changing the tranny mount back to a stock rubber one cause them poly ones can multiply vibs.

All that's gonna do is hide the problem for awhile, not fix it.

The splines on the yoke/output shaft are designed to lock up under torque, and not ride on the bushing. The bushing normally doesnt do much work. I would focus on the the drivewshaft and angle. An angle finder is cheap. If the angles look good, take your driveshaft down and have the balance checked with the new U-joints in it.

[bull]

This may sound dumb but make sure the tranny mounting bolts are good and tight.