I have a 2001 jeep cherokee with a 8.25 rear axle in it. about 6 months ago it started a slight but noisy vibration. I have changed front axle shaft u joints, inspected and changed bad front bearings, changed u joints in both front and rear drive shafts, greased the crap outta both slip yokes, and still have the vibration. A month ago I noticed that I got a lot of slap in the rear differential when I went from reverse to drive. So I pulled the diff cover off, fluid was a little colored, normal wear flakes in it, nothing unusual. I checked my gear lash from pinion to ring gear and am sitting at about 8/1000 of an inch. That is close to the factory spec if I'm not mistaken. I then noticed, that there is about 8-10 thousandths of an inch play in the spider gears that ride on the center pin. Not up and down, but the pin moves that much. Could this be the source of my agrivation? And if so, can I replaced just the spider gears, and center pin and be okay? I've done a few diffs, and don't recall that kind of play in the spider gears. Anybody help me out please?

I would start by removing the center pin and spider gears. than inspect them for any wear or damage and replace if necessary.

Yeah, gears should be tight. Make sure the carrier isn't worn in the bore for the pin too.

I've possibly got a similar situation - Lately I've had somewhat of a "wobble" noise coming from my truck, so I replaced the U-joints all around. There's no noise when the drive shafts are disconnected, and possible noise with just rear DS connected (might be amplified if there was weight on wheels?). I have the front diff torn apart right now so I haven't been able to isolate just the front and see if that is where the noise is coming from.

Anyways, I checked my rear wheels for play, and sure enough they move in and out laterally. Measured with a mic, its about .05 inches. Is that any reason for alarm or is that normal? I haven't opened the rear diff yet as I want to get the front wrapped up first. Chrysler 8.25" rear diff.

Thanks guys.

That's normal. It's the distance from the end of the axle shaft to the center pin and back to the c clip on the inside of the side gear.

I just changed both rear axle bearings in my 96 xj. Took my time and made sure I didn't disrupt spider gears. I placed pin and pinion bolt in as I did one side at a time minimizing the possibility of disrupting spider gears.Upon completion pin did not at first slide straight up and then it did.maybe it was me being tired and it was getting dark. Buttoned it all up and it didn't feel right on the test drive. felt like it eas in 4 wheel. I just replaced all the unjoint and didn't take it for a test ride before I did axles. Mistake cause now I'm not sure if it's from the rear or from joints.there is a 3inch RC in it with no try.Had some vibration ,nothing terrible.Now I put it up on jack stands and around 40 mph I get a growling whichh sounds like it's under my feet.Is this drive shaft vibrations? Do I need to drop transfe case. Any ideas please