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Discussion Starter #1
Hi All - Haven't used the Jeep much in the past several years but it'll be serving DD duty for the foreseeable future so getting it back into tip top shape. It's a 2004 TJ Rubicon. Front axles are leaking so I'll be replacing the inner seals, pinion seal, and installing outer axle seals while I'm at it.

Back in 2012 I put on 4.88 gears. I did the install myself on the rear then had a shop do the front bc I was starting a new job and didn't have time. Probably around 85k miles at the time.

I can't remember the last time I checked or changed the front diff fluid but now I only have 96063 miles (11k miles in 8 years... I know, embarassing) and just took it apart and its very dirty:

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I haven't done any mud since the gears were installed so I'm hoping it's bc the inner axle seals were not replaced when the gears were done, and rain/dirt just made its way in there, but also concerned the gears weren't installed correctly and I just haven't noticed. Here is a shot of the drain plug where there seems to be a fair bit of metal and sludge for only 11k miles.

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I'm hoping one of you gear experts can help me diagnose any potential issues with the gear pattern before I replace the inner seals and pinion seal. Based on what I can tell from research it seems borderline between good and pinion depth needing reduced.

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Also not sure what I think about those rust spots... is that normal?

Looking forward to hearing what you all think. Thanks, Ric
 

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Not a "gear expert" but know a couple and have helped with a few gear installs. That does seem like a bit more sludge than expected with those miles. Also, those rust spots look like surface rust and no big deal (probably from extended sitting).
 
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Your pattern doesn't look good in the picture but you cannot really tell untill you actually get some proper marking paint on them. Usually if you change the pattern after they are worn in they will make noise. Are they quiet now.
 

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Your pattern doesn't look good in the picture but you cannot really tell untill you actually get some proper marking paint on them. Usually if you change the pattern after they are worn in they will make noise. Are they quiet now.
I agree with the above statement. Need to run a pattern with gear marking compound applied to get a good view.

That said, you will get some sludge during the initial break in period. Has the fluid ever been changed after the install?

You will get more sludge with an improper set up.
 

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Discussion Starter #5
Thanks everyone... took forever to find some gear paint... finally found it at a Napa a bit further away (very well stocked compared to local O'Reilly's and Autozone). I put some Prussian Blue on 6-7 teeth.

Coast:
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Drive:
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From looking at gear pattern charts, seems to me the pinion depth is correct but backlash needs reduced. So I got out the dial indicator and backlash averages 0.015-0.017", which is high.

To rlenglish's point, not sure I should go messing with the carrier shims since the gears already have 11k miles on them. And yes, they are quiet now - no issues!

To answer JEEPINKC's question, I actually am not sure if the diff fluid has been changed since the install. My maintenance log says I changed the front diff fluid 500 miles ago in 2017 but it's hard for me to believe (I don't remember) due to the amount of sludge/metal.

Might be worth noting my front pinion has probably 1/32" of front/back slop but no lateral (side to side). I had already taken the pinion nut off bc I am going to replace the yoke (screw broke in it) so I tried putting the old nut back on to check preload but couldn't tighten to spec (my axles, brakes, knuckles are all off) so just tightened with the impact wrench (yoke held in place with a jackstand) and my in-lb dial indicator still doesn't even register.

All said, I think my plan is to replace the inner axle seals and pinion seal - as originally planned - along with the outer pinion bearing and not mess with anything else. Thoughts?
 

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If you are not hard on it, it should be fine. I wouldn't attempt to redo the backlash at this point since you have put some miles on it. If I remember correctly, the backlash should around 6-8 thousand.

I would also assume that the fluid has not been changed after the break in period. That is why you have so much "sludge" in there. I say put fresh fluid in it and roll on.

Just my opinion, others may disagree.
 

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IDK what I would do. If you have no pinion torque to rotate then obviously it wasn't set up correctly. You could leave as is and keep a eye on it or do a full tear down and setup. If you set it up properly the concern would be noise as the gears have already set in. Not saying it won't be quiet its just a possibility.
If you did tear it apart and set it up correctly, and it was noisy, would you live with it or put a new gear set in it? How much are new Gears? Should you just do it all now?
 

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Moab Outpost set up some new gears for me and they wouldn't warranty their job unless you returned after 50 miles for a gear oil change and inspection (which you paid for.)
 

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Discussion Starter #9
So I dug into it today and think the excess "sludge" is just sand/dirt that made its way into the housing, because the driver side inner seal is toast and the axle tube has about 1/4" of sand/sludge/mud/goo along the bottom. It probably just mixed with the metal particles and gravitated towards the drain plug in the earlier pic.

In this pic my index finger is the sand/goo I swiped from the axle tube and my middle finger is the sludge from the drain plug, which is relatively runny:
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John - to your point, yes that's a good policy and I hope/trust I did change my gear oil after getting them done as I'm pretty meticulous with these things - I just can't say for sure as it was 8 years ago and my maintenance log is just scraps of paper strewn about the house that I can't seem to ever consolidate.

As I was taking it apart I was trying to look for things that seemed off, but couldn't really find much. The upper left carrier bolt was missing a washer. None of the gear teeth seem chipped but I'll have to clean first to look for cracks. Here are some pics of the shims - I don't want to take the carrier bearings off but it just looks like a single shim on each side as opposed to any sort of stack.
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Anybody see anything wrong so far?

I am not really sure how to inspect the bearings themselves - any tips? My fear is the high backlash I measured is due to excessive wear on the bearings caused either by non-ideal setup OR the sand/dirt that made its way into the housing.

My plan is still to just replace the outer pinion bearing (and seal), install new inner axle seals, and reinstall the carrier as-is, but I'm going to paint the axle first, which should take a couple days. Then I'll measure pinion preload and backlash and see how it is. Figure if similar/better as now I'll just run it - unless someone chimes in there is a high risk of failure from too much backlash that could cause my diff/lockers/axles to fail, in which case I'd prob just pay the $300-ish to get a new ring and pinion set and new bearings/shims and hope the wifey doesn't notice.
 
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