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Hey all, so I have a horrible grinding noise coming from, what seems, my rear differential. It all started when I was driving my jeep up hill with my 4x8 trailer on the back (empty). I have 33" tires and I often have to drop from 5th to 4th when going up hill on the highway near my house. I managed to limp off the 2 lane highway to a small road where I tried to takeoff from 1st gear and it proceeded to grind. Initially I was freaking out and thought it was my tranny. Leading up to this event a week or two prior, I noticed an unusual increase in road noise and whining coming from the rear end but summed it up to me needing to rotate the tires.

(Backstory: I have a 97 wrangler sport with 120,xxx. Dude before me did little work at all to this jeep as far as maintenance goes. I lifted my jeep 3" budget boost and got new adj trackbar, adj lower front control arms, quick disco links and new wheels with 4" of backspacing. Had a little death wobble until I got the new tires/wheels with more backspacing and the steering stabilizer. Until now, I had little issues driving my jeep. )

I towed it to my father-in-laws and we took apart the diff cover and I inspected the spider and pinion gears. Looks like I have a good amount of wear in the teeth because the old fluid looked like silver paint :/ and some chipping. Not bad, but not great looking either. I haven't had much time to inspect anything else, althought I did try to take off in 4HI, which "worked" - - - still constant grinding but less volume, which makes sense considering the power transfer is cut in half. I could actually drive a few feet which leads me to believe the problem is behind the transfer case.

Question(s): Should there be any play in the drive shaft coming from the transfer case into the diff? If so, what is the likely culprit, given the info provided above? U joints or yoke/pinion seals? How likely is it that the axles could "go out" or shift?
I almost want to go get some washers and drop the Tcase .5" - 1" to see if the pinion angle improves my problem. That's the cheapest attempt at a solution thus far. I think this weekend, I am going to disconnect the rear driveshaft and try to drive in 4HI (essentially front wheel drive) then I'll know its not the tranny or tcase, atleast, if it doesn't grind at all.
If no noise, I'll probably end up getting a SYE and CV driveshaft and doing the install myself. .....any thoughts?

My gut tells me that I have bad pinion angle and I wore out my u joints fast, especially running the larger tires and lift. My driveshaft is about the rustiest part on my rig! I really don't want to rebuild the Dana 35. I think even if it's the u joints, I still want the SYE and CV driveshaft combo (about $500! ouch).
 

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Welcome to the forum. You didn't say which rear you have D35 or D44 but the 35 is the most common in the TJs and also the weakest (we have 2 of them). You need to completely disassemble the rear end. Hopefully your ring and pinion are still good but if you have metal in the oil, something is failing. I have been in 10 or 12 D35s and a common failure is the boss where the carrier bearings ride is soft and will wear to the point that the bearings are loose on the carrier. Also could be failed axle bearing and/or pinion bearings. If you have any play in the pinion, either the pinion nut is loose or you have pinion bearing failure. If everything else is good but the spiders and side gears, you need to at least replace them. Also check the cross pin bore and make sure the pin is not wobbling in the bore.

As you said, the noise still may not be in the differential but sounds like it's in that area. When we bought my son's 97 two years ago, the Jeep had been in a mild accident and was parked for several years. When we test drove it, it had a dry grinding noise in it that sounded like a dry wheel bearing but actually turned out to be a very dry and stiff u-joint at the differential that was making the noise. We tore the rear end apart and it had problems too. The carrier was still good but the internals (spiders and side gears) were bad, both axle bearings were bad and the axle shafts were worn to the point of not being reusable where the wheel bearings ride. I had replaced my rear carrier in 00 with a trac loc 2 years prior so we just used the internals out of my old carrier and my old axle shafts to get him back going.

Good luck with it.
 

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