Trying to chase down what is causing vibrations in my XJ I put it up on stands yesterday and checked the U-joints.

There is a tiny bit of play...and I mean tiny - like 1/64 of an inch. You can just barely see some movement when holding one side of the joint and trying to move the other.

How much play will produce noticeable vibrations?

 

should be absolutely no play in the u-joints.

 

Correct me if I'm wrong but you shouldnt have any play in your u-joints. Could be a sign that the needle bearings are going bad. Just replaced my u-joints in my front shaft (all three) because it was causing some vibes, but mine had at least 1/4 of play if not more. All joints had play, one joint had all the needle bearings missing off one side of the joint. Now I'm replaceing the joints in my front d30, have play in those also.

It can cause vibes, the play in yours may be small but turning while running and that little bit of play will cause vibes. It will only get worse as you drive it. Go to "Tom Woods" web site he has good prices on joints. I got some and there very nice.

 

The vibration comes on at about 35 MPH then kinda falls off a bit but never disappears.

I really have to twist on the u-joints to see any play whatsoever. I'm hoping that is where the trouble is, though. They are cheap and easy to fix.

 

The front joints I changed was a pretty easy fix. Rented the tool from the parts store, I bought new straps, never know if the old ones are stretch or not.

The axel joints I'm using a hammer and drift. The tool wouldnt budge those caps at all (i also broke 2 out of 3 bolts on my hub.....PB,PB,PB is all I have to say).