Posted on NAXJA but I wanted to see what y’all over here think too. Need some thoughts on what could be causing this faint vibration/grumbling noise I’m hearing after I had an SYE kit from 10 factory installed and new DS. It’s going back to the shop but since they couldn’t figure it out the first time I left it with them I’m trying to exhaust all other possibilities myself before they crack open the tcase again and look.

97 XJ 2” lift closer to 2” 1/2 in the rear. General spring HD leafs with a JKS boomerang.
The noise is throttle dependent. It goes away as soon as you take your foot off the gas. Kind of sounds like a brake dragging. You can feel the vibration through the floor boards. It’s pretty constant at all speeds, is more noticeable at lower speeds and when you really step on the gas.
I brought my pinion angle up to about 0-1 degree with a 2 degree axle shim.
Tried pulling the front ds. Tried pulling the rear and driving in 4hi and still hear it, sounds like it’s coming from the tcase. Tried putting the front ds in the rear. Changed my trans mount. Motor mounts are fairly new. Yoke/output shaft on the tcase doesn’t really have any play, maybe an 1/8 of rotational play in either direction. Zero movement with ds connected. What else could go wrong with a SYE install inside the tcase? Doesn’t seem like chain is slipping and I don’t hear any hear noise when I turn it by hand. Opened diff and gears seem ok, they’re fairly new too and oil looks good. Other thoughts appreciated, it’s going back Tuesday but I don’t have much faith in this shops abilities.

 

Sounds like your rear driveshaft angle is wrong. Zero degrees would be for a vehicle with a rear coil spring suspension. With leaf springs the angle should start out at 2 degrees down to allow for the lift of the pinion yoke which would put the driveline at it's proper angle.

https://www.adamsdriveshaftoffroad.com/angle-pictures/

https://forums.4wdmechanix.com/topic...eshaft-angles/

 

It made the same noise before I put the shim in that’s why I figured I needed to bring it up closer to 0. But I’ll take it out and try again. But it still makes the noise when driving in 4hi with the rear DS removed, although slightly different. But it really feels like it’s coming from the tcase.

 

With no driveshaft in the rear (I missed that part!) and the noise still there it does sound like a transfer case issue. The sound will be different with the shaft in as it will increase the volume. I see your taking it back to the shop but if you would want to you could remove the rear shaft and with all wheels off the ground and the t/c in 4hi put a stethoscope (screwdriver would work) against it and listen. As to what could be the problem with the t/c? Could be quite a few things. There is an oil pump that if not correctly reinstalled would cause a problem for sure.

 

Thanks for the advice. I’ve been messing around with it today, measuring angles. After putting the new trans mount it actually raised everything up a bit because the old one was so worn. Thought for sure that was it. Nope. With no shims my pinion angle is about 5. And there’s definitely driveline vibration.
A 4 degree shim put me over, and also had vibration.
So I went back to the 2 degree shim and re measured, and my pinion angle is about 2 degrees now actually. There are no driveline vibrations, but there is still the grumbling sound I described earlier. So yea I think the shop will have to take the transfer case apart, again.

 

I'm 3 years into a SYE on a 91'. Searched high and low for answers. Changed pinion angle so many times that I can still do it in 45 minutes. New drive ("propeller" per MOPAR) shaft, transfer case, new transmission. Never did find an answer. Very noisy and vibes at 35. Four garages, three high profile, high skill 4x4 shops. Just living with it. I have $15K into the XJ. Hate it now. Good luck.

 

The bearings that came in the NP242 rebuild kit I used were very rough, and likely loud, in comparison to the Timken Input and Front Output bearings I used instead. The Rear Output bearing that came with the SYE was smooth like the Timkens, so no need to replace. Another possibility is them nicking or deforming the case when installing the Front Output Support Bearing. It's a blind bearing and I just let sleeping dogs lie on that one...

 

dang, I’m sorry to hear that. I hear ya though, I’ve changed the pinion angle and re measured at least 10 different times. Good luck to you as well

 

good to know thanks, I’ll mention that to the shop when I drop it off. Is there a way to test bearings? Is it bad to drive on them if they make noise like that? Assuming that’s what we’re dealing with. I’ve been driving/pushing it pretty hard this weekend almost hoping something fails or breaks so i can at least know what the problem was. So far nothing has changed and other than the noise/hum and vibration it drives fine.

 

I wouldn't say there's any harm in driving on them. When I held them in my hand and just spun them, you could feel the ***** in the ones from the kit. Kind of like concrete seams on a highway. Da-Dunk, Da-Dunk, Da-Dunk, ... The Timkens I used instead were smooth as butter. Not a bit of roughness to them, "smooth as glass"...

 

If it makes you feel any better, mine works 100% better after the rubber plug popped out (NP242-only thing) and all the oil drained out over the course of a 2 hr drive. Shifts great now...

 

You guys put new ujoints in (correctly)
i often find if a noise sounds like its coming from the rear its actually on the front