The drive shaft u joints have been replaced and I still have a perceptible vibration over 50 MPH. Could it be possible that the drive shaft need to be rebalance?

It's possible. Check the the Drive Shaft tube for any visable damage like dents. If it does then you will obviously need to replace it.

Another thing to look at are your tires. Tires that are out of balance will cause this as well or poor tread wear.

Z Rule, this problem happened only since the u joints have been replaced. Tires are new.

Have you checked to make sure the bolts that mount the drive shaft to the differential are all properly tightened? It's a tight fit getting a wrench in there. Were the tires replaced before or after the drive shaft u joints?

Tires were replaced before the u joints.

Did you check your motor, trans and diff. mounts?

I would make sure they are tight the bolts for the shafts, and also check that the ujoints were properly installed and in correctly.

I would be checking there first and foremost for any problems, since you didnt have this problem before installation.

Good luck.

I had a vibration on my '73 and had the u-joints replaced by the only shop in Denver that still does that. After installing I still had a vibration, but not as bad. Turns out they couldn't get the good (spicer I think) u-joints so settled for what was available. There was a small amount of play still. I took it back a second time and they ordered the good joints and now all is well. In all fairness to them, they were as surprised as I was.

To confirm if you have an issue with the u-joints, get under the car and put one hand on each side of the joint and try to wiggle it. If you can feel ANY play at all on new joints you have an issue and probably should go back to the shop that put them in. Be careful not to confuse this with play in the drive shaft from the tranny and diffy. I found I had to turn the shaft so that it was sort of between the limits of its motion, and then holding it still with that hand try to feel any movement on the other side with the other hand. Also try to move it up and down, not just rotate them. That was the issue with my first set.

Good luck! Drive line vibrations are a pain.

OK so you say this vibration started AFTER you installed new U Joints and it was fine before?? It's got to be something with the new U Joints then. Double check that all the bolts are torqued to factory specs as mentioned by Ken.

Plus I wouldn't rule out the drive shaft itself. They need to be handled extreamly careful as it doesn't take much to knock them out of balance. Also check to make sure the drive shaft is clean because anything like undercoating overspray, mud ect. can cause them to be out of balance.

Best of luck.

Thank you to everbody with your comments about my vibration problem.

All the bolts of the differential carrier and supports have been retorqued to specs and the problem is now solved.

Glad to hear it was something simple