letsgomuddin

'01 XJ with 29 spline C8.25 rear. Going down the road at speed I get no noise, but if I let off the throttle for a sec I get a growling noise for an instant. Then I get it again as I get back into the throttle. On level ground, I can feather the throttle and make it growl constantly. Has to be gear noise as bearings would make noise all the time not just upon load changes. Any thoughts as to a cause?
P.S.
Fluid is new 80/90w hypoid

SeriousOffroad

Could be u-joints, could be pinion bearings.

letsgomuddin

Not u-joints, pinion bearings I would think would be a constant noise not just under load changes, plus I have no leaks or up and down play that are usually associated with bad pinion bearings

may pop

Or carrier bearings. Either one will cause the noise you are hearing. It wont feel loose either. Common problem.
Ron

adgmobile

I have this exact thing, going around 40ish and I let off throttle and it is a dull grinding type noise.

Hard to tell, but I think mine is coming from the front. Axle also clunks when I accelerate from start on front drivers side. Ujoints and Wheel bearings are new. Does that single out the pinion bearing? And is a new (junkyard) axle the best fix?

*Well took the rear diff cover off this afternoon, needed new oil BAD anyway... Most of the gears look good, but the top one of the 4 that are 'crisscrossed' for lack of better description, the small ones not the large pinion or the spiral one (sorry for non-technical description) can bbe moved about 1/8 inch up and down with my fingers. Could this make the noise? and how bad is that, like do I need to get another axle or rebuild?

Also I don't mean to hijack thread but OP is describing *exactly* what I came here to find out on an 01 with 8.25 so figured I would post here.

letsgomuddin

UPDATE:
Finally got around to pulling the diff cover this morning, noise is due to the worn ring and pinion gears and super sloppy spider gears from the high mileage (260k). It became Snapon locked, problem solved!
(at least till I find another axle anyways)

adgmobile

Could you describe how sloppy is too sloppy for spider gears? I pulled my diff cover, and, damn, the fluid was total funk. there was some play in one spider gear, it went like 1/2 milimeter or so up an down, not turn-wise, but like sliding on its shaft.

On the other hand, there was a good amount of play in ring/pinion. But the front ds is off, so it turns the yoke a bit.

I'm thinking the bearings on the yoke are shot, maybe the ones for axle shafts too... just curious about the spider gears, I am learning as I am going here, I have zero experience with diffs. For what its worth the gear teeth looked fine.