On my 2001 Sport (4.0, auto, 231, no lift, street tires) I'm chasing a vibration at 60-80 MPH. I originally thought it might be the hubs since I heard they develop a flat spot and cause issues. Well today I decided to pull the front drive shaft to just see and the vibration went away. I checked the u joints and they seemed good (but looked like the originals). Now before I replace the joint what else should I check into?

 

Take it to a drive line shop and get it balanced.

 

Yep that's my plan, I want to make sure 100% before I spend the coin.

 

Yes, I could push it at the slip yoke and it had some play. It is worn out if it is not tight at the splines/slip yoke area. Any play will cause a lot of vibration since it always turns.

 

Any play in the front yoke? There should be none. Normal wear in the pinion bearings can cause movement that will wear out the pinion seal and possibly cause vibration.

 

I had a driveshaft shop rebuild the double u-joint part of my 96 front shaft

 

I had the same problem on my 93XJ. I removed the drive shaft and took it for a test drive, everything was smooth as silk. I replace the 3 u joints. I had to also replace the centering yoke that was behind the double cardon u joints. It did help a great deal but there is still a small vibration in 2WD but OK in 4WD. 3JeepGuy.

 

I had to replace my front shaft a few times on my old TJ, the double cardan end would go out on it.