strangetimes

Hi everyone, I've used the search function and cannot find any threads specific to what I am looking for so...

Just purchased a 98 jeep xj with 166km's privately. Got under to give a going over.

Checked rear diff fluid. It was dark, so I figured I would change it. Removed diff cover, drained oil. Sludgy. Began cleaning ring gear and noticed odd wear pattern on the outside edges of the teeth as well as small gouges on the outside edge inbetween the teeth. I will post a couple of pics, but it was very difficult to get a good close up shot without moving the camera too much.

Note: Whoever last had the cover off used gobs of rtv silicone gasket and there were little globs on the end of a few diff cover bolts. One of these globs seemed to still be quite soft and not rubbery, leading me to believe that the cover had been replaced shortly before I purchased the jeep...

Is it common to have paint pen writing on the ring gear?

The front diff fluid was pretty clean, but there was a lot of filings on the magnetic fill plug. And one of the front diff cover bolts wasn't even threaded all the way in. It had about 3/16 of thread left before even touching. Wouldn't have stayed in for too many miles like that.

I am not very familiar with the diagnosing and building of rearends, but the gouges look fresh, and the wear on the outside is also fresh as there is a slight "lip" to one side of the rub mark.

Maybe everything is fine, but I have a suspicion that for some reason, the rear gears (maybe front too, haven't had the cover off) were swapped out and installed incorrectly and there isn't any clunking, howling, vibrating because they've only been in for a few days, but within that time the rear diff fluid became almost black.

I don't know why anyone would need/want to swap gears with such low kms, so maybe I'm just losing my mind. I'll be taking it to a mechaninc anyways, but I thought I would share.

Any insight would be great.

If you look closely near the right hand side of the images the outside of the gears are shiny. You can't tell in the pic, but just on the edge of the shiny area there is a sharp lip.
Thanks for lookin.

andyg

Those gouges are unexplainable to me. Nothing should ever cause that unless a gear tooth broke off and crashed between the ring and the housing.

I would have your mechanic check the gear pattern using pattern grease and see how the ring and pinion are set up. The black oil could just be from age.

strangetimes

Thanks for the response. hmm, I didn't find any metal chunks in the fluid, although when I drained it initially I wasn't really on the look out for any. That's a great point though.

strangetimes

The previous owner had been driving with the spare (more tread) on the rear driver side. Maybe this has something to do with it.

djb383

Probably not, open diffs easily compensate for different tire diameters. Kinda hard to tell in the pics, I'm not sure what's different?

strangetimes

What's different with mine is that if you look at the right hand pic just above the letters written with paint pen, there is an edge of the teeth that is shiny. On close inspection there is a small lip on one side of that shiny edge similar to what happens when you round off the head of a bolt with the wrong size wrench. Also, its tough to see in the pics, but there are also gouges inbetween the teeth.

strangetimes

Can also be seen on the two last teeth on the right hand side of the first pic.