8.25 Axle Clunk - Excessive Wear on Side and Spider Gears?

[terrawombat]

I'm chasing a driveline clunk in my '01XJ that serves as my all-purpose daily driver. Ever since I've owned the thing it has had a noticeable driveline "clunk." Anytime you're cruising and you tap the accelerator, it will "clunk". When you slow down and come to a complete stop, you'll hear and feel a "clunk." Changing from reverse to drive (and vice versa) nets you a nice "clunk." The "clunk" has become more pronounced as of late so I decided to finally chase it down. It's been 30K miles since I last replaced the rear diff. fluid so I decided to pop the cover off today and do a full inspection of the gears. No missing teeth, but I did observe a lot of slop between the side and spider gears. I could rock the side gears on the center pin side to side and there seemed to be an excessive amount of backlash between the side and spider gears, but honestly, I don't know too much about differentials to know what is acceptable and what is excessive. I snapped some photographs of the gears in hopes that some of the more experienced people on here can school me and tell me what they see.

 

 

With the spider and side gears out, the ring and pinion backlash seems to be very, very small - although I do not have a dial indicator to tell me the exact number. I'm hoping I can get away with replacing the spider and side gears and have a much tighter and non-clunking rear end.

[jeepsouth]

How are your u-joints? :cheers:

[terrawombat]

Although they look original, they passed all of my standard u-joint excessive wear tests. They are still extremely tight.

[Incommando]

It is apparently possible for the adjusters on the Chrysler corporate axles to "back off" causing excessive play in the differential and causing a clunk like you are describing. Re-asembling the diff and properly setting the adjusters may take care of the issue. Aussie lockers, for example, blames excessive wear in the cross-pin, which is about a $15 replacement item, and also cites the adjustment issue as reasons for an unusually high failure rate for their locker in 8.25 axles.

 

Granted, the above information was told to me by an Aussie rep. in explaining why the locker in my KJ failed and may be so much hot air, but it seems possible.

[jimoshel]

At least replace the pin. You can see the wear on it. The gears, hard to tell but they look worn in the pics. Go to the friendly parts dept joker at the dealership and ask him to lay a new one on the counter so you can compare them. Very minute wear on a gear translate to very loud clunk when running. If I were doing it on mine, I would replace the pin, keep the gears, assuming there are no rough wear on them, and reset the adjustment. :wrench:

[Motion Offroad]

We've seen the carrier bearings fail on the 8.25" on more than one occasion. This will cause a "pop" or "clunk" sound as well. Our assumption is due to the adjustors coming loose, which allows for movement in the carrier is the reason for failure. You may want to just look at the bearings closely while you have it apart and see if they are still good.

 

Be aware the the 8.25" is considered a "noisy" axle. It'll produce a decent amount of sound even with everything setup properly and within spec.

[terrawombat]

Thanks all for the information. Just so that I'm clear - the carrier bearings that I should be inspecting - these are the ones on the sides of the differential? I only have the FSM to go by for removal procedures and they refer to those as differential side bearings. In order to get to those, I would need to remove the adjusters and bearing caps, which would lead me to believe that I would need to setup my diff when it went back together. Certainly don't have the experience and the tools to do that...but I DO have a spare, good 8.25 axle if I REALLY screw up...I'm just trying to avoid swapping in a whole new axle to this Jeep.