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Not your normal vibe thread

summitlt

NAXJA Forum User
Location
Maine
99 XJ NP231

Bastard pack with shackles in the rear. Pinion is 1 degree down without the tcase drop and they are the same angle with the drop in.

Tried a known good driveshaft with no change. Vibes start at 60mph and become unbearable over 70.

Lift in the rear is a touch over 2"

What am i missing?

No change with the front driveshaft out and with the rear driveshaft out its fine.
 
when did they start....after what mod. How can the pinion angle be the same (relative to the driveshaft) with and without the T-Case drop? What's the age/condition of the driveshaft u-joints?
 
Your pinion should be 2-3* down, and i would shoot for 3*. 1* down is too little, and being at the same angle will definitely cause vibes.
 
Might be a bad pinion bearing. See if you can shake the drive yoke up-down/side-to-side with the driveshaft removed. Standard dual u-joint driveshafts should have the pinion and tcase output angles running parallel (0-degrees), CV driveshafts should run with the pinion angle down, relative to the tcase output, 1 to 2-degrees.
 
Standard dual u-joint driveshafts should have the pinion and tcase output angles running parallel (0-degrees), CV driveshafts should run with the pinion angle down, relative to the tcase output, 1 to 2-degrees.

agreed^^

I don't see where there's a SYE on the transfer case-- you want same angle at both u-joints to alleviate vibrations.
 
Sorry, my above statement was incorrect because that information is for a double-cardan style shaft. You don't say what kind of driveshaft you're running but it sounds like probably a stock one.

In that case, you want the pinion angle to be the opposite of the output shaft under acceleration (so if the output shaft to driveshaft difference is -2, you want to end up at +2 with the pinion to driveshaft). So you're probably pretty close with -1 or 0, since the pinion will rotate up 2-3* under acceleration.
 
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