Front drive shaft vibrating

The front is at 5.5" and the front driveshaft has vibrated since I put the 4.5" RE kit in. I have 3/4" spacers under the T-case at the moment although I may take them out next. The vibration is only there from about 55mph up and goes away when I put it in fulltime 4x4. The XJ is a 94 model and has 110,000 miles on it. I have adjusted the upper control arms so I have 0 degrees on the pinion uni another words the DS is inline with the diff pinion. I have removed the front shaft and the vibration is not there.

I suspected that the vibration was coming from the small amount of slop in the slip joint. I took the DS in to a engineering shop and they said there is nothing wrong with in and that it doesnt need rebuilding. I have tried pulling the slip yoke off and turning it 90 degrees and refitting it but it doesnt help. I am also running all terraines. It seems at this stage as there is no fix for this. Any ideas.

You must allow for torque. Drop the pinion angle a couple degrees so it is straight when you are on the road. It will climb from rolling resistance even in 2-wheel drive.

I have had it at about 2 degrees down and it still vibrated above 55mph

cdhowell said:

You must allow for torque. Drop the pinion angle a couple degrees so it is straight when you are on the road. It will climb from rolling resistance even in 2-wheel drive.

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That doesnt apply to the front axle!

Using the TC drop makes the front angles worse,get a SYE kit and remove the drop kit!

Forgot to mention I already have one. I dropped the T-case at one stage to reduce try and reduce the harmonics in the vehicle.

Remove the Tcase drop.Install washers a couple at a time(were the tcase drop is)to see if that helps.

That did it, finally nomore vibes. The problem all along was the DS I had built by Hardie Spicer here in Australia was built using no name Korean parts. I have been chasing this problem for 18 months.

So the engineer shop that told you the DS was fine and did not need rebuilding was full of sh*t? Do you still have the t-case drop spacers in with your new DS? Ouot of curiosity, what degree of caster do you have in the front?

No sorry I meant the rear double cardan DS I had built when I lifted the XJ 18 months ago was defective in some way. Not sure what the caster is now but is drives very very well considering the size of lift. Front DS is not vibrating now that I have taken the T-case spacers out. I had left them in because I was trying everything but was actually the defective rear DS. I had a front DS lenghened and fitted in the rear and it worked perfectly no vibes that is.

xjdavid1 said:

No sorry I meant the rear double cardan DS I had built when I lifted the XJ 18 months ago was defective in some way. Not sure what the caster is now but is drives very very well considering the size of lift. Front DS is not vibrating now that I have taken the T-case spacers out. I had left them in because I was trying everything but was actually the defective rear DS. I had a front DS lenghened and fitted in the rear and it worked perfectly no vibes that is.

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Gotcha. My front is vibing at around 55MPH, that is why I ask. I took it completely out for now. I might try taking out my .75" t-case spacers like you and see if that works. My caster is 6.5* so I might have to tweak that again if I take the spacers out, don't know.

Yes take out spacer and adjust front pinion angle to zero if you have adjustable arms. I wouldnt worry about caster to much as mine drives fine with zero degrees on the front diff uni , pinion straight with DS. I assume you have a SYE kit and DC DS