driveshafts are balanced with either stick on or weld on weights. (i say weld on, more like tack on) be sure you didnt accidentally knock one (or 2) off while changing u-joints. this doesnt really explain why there are no vibrations when under a load but something very easy to over look. it doesnt take much to make a driveshaft outa balance and cause crazy vibrations (especially at 60 mph). hope this helps

 

Had an afterthought today. When I went to pull the drive shaft to regrease the Ujoints and check the straps it didn't come off the Jeep very easily. The slip yoke seemed to be stuck, and there was no play in the driveshaft. I had to tap it with a dead blow hammer and roll the Jeep back and forth to get it to drop. Upon reinstalation I placed a small amount of grease inside the slip yoke to help it slide back for reinstalation. I got to thinking that perhaps the problem is with the slip yoke itself. Perhaps there isn't enough grease on it to allow it to slide back and forth smoothly. But I feel like this would be too simple, and if this was the problem that I would experience the issue more when drive line angle was changing, not when I'm traveling at a consistent speed on the interstate. Thoughts?

One more thing, once the drive shaft was out the ujoints were able to move incredibly easy, way easier than they were new from the store. If they had not been greased could they have been worn out after driving a few hundred miles?

 

That could be your problem, I don't think the u joints would ware out but if they were bone dry they might show some shiny spots. They come with enough grease in them to go a couple of hundred. Don't complain about an easy fix I'm sure you'll pay for it somewhere down the line.

 

It was the c-clips.....all fixed now!

 

What was it about the c-clips? I've got a similar issue with the tom woods shaft I put in the rear...

 

 

make sure you didnt bend the ears on the shaft. if they are tweaked at all from a vice or hammer or whatnot, it will throw your shaft slightly out of balance making it vibrate at a high velocity. happened to me and then my neighbor (35 years being a certified mechanic) mentioned that could be the cause and i straightend them out (had vised them too hard, rookie mistake) and it eliminated the vibes.

 

Do you mean the ears that hold the u-joint? That shouldn't be the case for me as I put in a new shaft and didn't touch the u-joints.

Out of curiosity, how did you determine your ears were bent and how did you determine what straight was?