here is my front ring gear. It was installed two years ago. I opened the diff to deal with a seal leak. I see lines in the gear teeth running parallel to the teeth, it is normal? I also found a good deal of very fine sludgy powder in the bottom of the diff, very fine, and stuck to magnet.

Is this gear set up wrong?

You need to get a dial indicator to determine the amount of play. Then some

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to see how they are mating.

And a little more history. What brand of gears? Who did the installation? And why-- did the previous diff blow up (consider remnants left behind)?

Sierra gear 4.11 me and friend set up gears, he has done several, they all had good paint mark patterns upon testing after set up. Reason for the rebuild two years ago.... the prior owner got water in it and sat for ten years, so the arb got new parts to replace rust damage and a new set of gears and bearings.

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In the photo it looks like there's particles all over it. Lines are usually from contaminants. That looks like a lot of wear for just a couple years. Measure the backlash it might be too tight. IIWM I'd pull the carrier and give him a good bath.

its all coming out, New axle seals and arb slip ring seals should arrive this weekend, then it comes apart. I have the axle oil leak, and air leak of the arb to fix when I found this. backlash, I think it was about 0.005 or .006 inch, we measured the other day. Certainly was a good deal of fine powder fine sludge in bottom, both on magnet drain plug, and filling up that valley in the casting at bottom near the cover mating edge. It appeared to just stay sludged at the bottom rather than be distributed in the oil. Usually i would expect fine hairs of metal on the magnet, not this fine powdery stuff. weird. And yes the oil was drained and refilled at least 2 or 3 times since it was rebuilt. Never ran low, nor abused. Have manual hubs so this baby is not spinning when on the highway, only when off roading when I decide to lock hubs. Maybe I guesstimate 800/1200 miles of driving with hubs locked. So this diff has low miles despite 2 years of use.
Anyway We will see what the bearings look like, If they are toast, then I will likely decide to regear to 4.56 as I got 33 inch tires. But that means doing rear end work too. I want to travel, wheel, not work on it all the time. oh well, it will be better for it.
I also will do a paint pattern again on it, just to check, I do have photos of the set up pattern to compare with. it that looks good, bearings ok, then I will replace seals, and keeping on eye on it. sound like a good plan?

So there was a water leak, now you have a seal leak, a destroyed ring gear in ~1000 miles, metal dust despite multiple gear oil changes and potential a/both bearings fried.

I would strongly consider the casing is bent, or one of the axles. IIWM I would get another axle assembly (avoid XJs in front end collisions if possible).

oil seal was partially folded over. examined axle and see the dia was reduced after the splines, then increased via a step, given the oil seal design it will fold over itself easily when slipped over the step in the axle., one brand of oil seal I tested is more susceptible to this verses the other. ( profile of the rubber differers, the good one is shaped as a ramp, verses the bad one) The original axle shaft did not have this dia. change and step, so it is not a problem on the original axle (I have the disconnect axle eliminator type axles, aftermarket)

bearings look ok.

still need to pull the arb apart to see if the piston seal is good or not. I need to pin point the air leak. The copper pipe appears fine.

The parallel lines on gear teeth appear to be machining marks, and are high lighted by the black oxide coating on the teeth being worn off the ridges of the machining marks.

here is pattern ran today ...

Still kinda left with this if you're saying there is -0- wear on the pinion:




I would check the backlash in lots of positions, which probably would show up misalignment or tooth damage

If you use high x magnification and strong light, I expect you may be able to observe whether wear is abnormal or not on the gear teeth

The ARBs are pretty notorious for leaking out the two O-rings on the carrier

test reveals the air leak is internal to the diff, the bonded seal perhaps, not the slip ring seals. I read that arb had a bad batch of bonded seals around the time I got this one.

Well how can that be, since