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98 xj driveline noise.

sams88xj

NAXJA Forum User
Here we go. Long time browser, haven't posted before.

Vehicle -
1998 Jeep Cherokee Sport
ATK reman 4.0 ~ 4k miles
4.5" RC lift full suspension with adj control arms ~ 500 miles
33" bfg at ko2 balanced ~ 500 miles
SYE with 6* shims for pinion angle - within 1* of DS
New ujoints
New wheel bearings

After installing the lift (previously had 3" with age) I had a thumping driveline noise. Assumed ujoints/driveshaft due to pinion angle being correct. Replaced all ujoints and centering joint in double cardan. That seems to have alleviated a lot of the noise (or maybe all and I'm encountering a different noise all together now). However under acceleration at any speed while in gear I am still getting a thumping driveline like sound, that seems to be coming from the rear, but can also be heard quite well at trans tunnel inside vehicle. (No carpet). I am stumped.

The front driveshaft has been removed.

Any help would be appreciated on where to start next.
Any other needed information I missed let me know!
 
Checked the transmission mount? Rubber good and the nuts tight?
Is the slip joint tight? Does it have enough engagement?
Axle u-bolts torqued to spec? They can loosen, after a spring install, and should be re-torqued after 50 miles or so.
 
U bolts are torqued to spec. Forgot to mention trans mount was replaced about 1k miles ago. Had the tcase shifter rattle, so I replaced the trans mount before learning of the tsb.
 
The pinion is 1* down from driveshaft, I replaced all ujoints on rear driveshaft. There is no noticable play at the pinion with or without shaft in. I will finally have some time this week to put it on jackstands in gear and see if I can narrow down where it seems to be coming from.
 
no problem, I just try to share any weird stuff ive had come up nd make noise on mine. Another thing to check, is your exhaust tip, they can tap the shackle sometimes, or all the time if you have aftermarket shackles. but a loose crossmember was causing a noise similar to what you are describing on mine. I also ditched the factory linkage setup and went with boostwerks linkage, works way better
 
My front DS makes one hell of a racquet. After messing around with just about everything I've finally figured out the slip joint (yoke side) is just plain worn out. Could this be your issue? To test mine I grabbed it at the end of the yoke (closest to the slip joint) and shook it like hell. There's side to side play in it. All my u-joints are tight as can be. With the DS pulled mine is smooth as silk.
 
no problem, I just try to share any weird stuff ive had come up nd make noise on mine. Another thing to check, is your exhaust tip, they can tap the shackle sometimes, or all the time if you have aftermarket shackles. but a loose crossmember was causing a noise similar to what you are describing on mine. I also ditched the factory linkage setup and went with boostwerks linkage, works way better

Mine was doing this as well, but in mine it was obvious the exhaust was hitting the shackle.
 
Well I had some time this past couple days and got a chance to lift the jeep and do some more inspection.

The vibration and sound both go away with the load removed. I lifted the front with the rear shaft taken out and put in 4h, no signs. Lifted the rear in 2wd and no signs. So it appears it is only under load.

While inspecting further I may have found the culprit however. My rear driveshaft seems to have a small amount of play that sounds as though it's coming from the joint where the 2 pieces come together under the boot. I put my phone in the jeep and pushed on the shaft, voila, exact same noise I'm hearing while driving.
 
could a worn slip on the front shaft cause a good vibe around 60-70? cuz I got one that gets rough around that speed, SYE, adams offroad, front end rebuilt, still stock driveshaft
 
Does your rear shaft have a cardigan joint? My wife's TJ had a similar noise under acceleration and it turned out to be a U joint in the double cardigan section of the drive shaft. Even though it had no play in it at all. Stumped me for the longest time because I'm use to a Drive shaft having play when a U joint goes bad.
 
mine has a new adams offroad driveshaft. I have a H&T SYE which causes a lil bit of vibes, but was fine, when I leveled the front out with the back of the jeep this vibration popped up
 
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