Rebuilt Rear Diff - Metal dust in Oil

2.5 Gen TRDOR, 8" factory e-locker rear

I recently had my rear diff rebuilt - I pulled the diff myself and took it to a local shop to get the work done. Only the bearings/seals were replaced, same ring & pinion used along with a solid spacer.

Anyways, I changed the fluid after 800 or so miles and the fluid came out silvery throughout with metal "paste" accumulated at the magnet. I thought this was somewhat normal for the break-in period, ect didn't think much of it. Put fresh oil in it and moved on.

150 miles later curiosity got the best of me so I drained the rear diff oil again. same outcome with silvery fluid, almost like a very fine sand-like consistency with the metal particles, magnet covered in metal paste again. Put fresh oil in it again, only this time a bit concerned with what's going on

Changed the diff fluid AGAIN after 100 or so miles and still the same outcome with the oil.

Is this normal break-in behavior for a diff that's been rebuilt ? 3 oil changes and I'm still getting metal dust in the diff oil. Wondering if there could be something else going on. Any diff experts out there have thoughts ?

 

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If it made that much glitter in only 100 mi something definitely isn't right.
Is it making noise?

 

@gearcruncher might be able to chime in on this

 

making ZERO noises. Driving quite smooth actually.

 

How well did you clean the axle housing including the tubes? It’s a lot easier to leave a lot of old residue than it is to actually get it clean.

 

That doesnt look right at all. Did you call the shop who did the install?

Side note: I love the mouse pad as a worksurface

 

I cleaned the axle housing pretty good, now that you mention it I don’t think I cleaned the tubes at all.

Have the day off tomorrow and thinking of pulling the diff to inspect/clean. Anything in particular I should be looking for? Not sure what kind of smoking gun I’d be looking for

 

If you can wipe with a white cloth and it turns grey, it’s not clean.


Did the original oil before the rebuild look a bit like anti-seize?

 

Actually pretty normal, especially if you had a failure which is why the 3rd member was removed.

Chunks on the other hand.........bad juju.

 

Inspect the wear patterns on all the gears !

looking for abnormal wear patterns .

Not screaming is a good sign.

 

Yea it did. When I drained the oil prior to rebuild I found glitter and metal chunks. When the shop took it apart they found one of the carrier bearings had called it quits

bad bearing



chunks I found in the OG oil

 

this is how the wear pattern looked before I threw the rebuilt diff on. I don’t really know how to interpret this but I’m aware that you can tell a lot by the paint pattern. Does this look normal?

 

what makes you say this is normal? So is it ok to roll around with glitter in the diff oil ?

 

First of all, there was still probably a ton of fine ''glitter'' left in the axle tubes and it takes VERY little to discolor the gear oil. You'll also almost always get some very fine particles [which is what I see on the magnet] when you initially install and run a new 3rd member. It may be set up properly but it still has to wear in.

I sorta consider it to be like antiseize, one teeny tiny little dab goes a long way when you get it on something you don't want it to get on. It's also way you should change gear oil when hot and right after using it before some of it drops out of suspension.

Grit and chunks, BAD, particles you can't even feel if you rub you fingers together, pretty normal. I'd personally like to see a little bit more contact between the ring and pinion gears but it's likely fine. It's pretty easy to set up a 3rd member nicely on a bench VS doing it in the axle housing.

 

appreciate your input. I wasn’t doubting you in your comment, I want every reason to believe I’m not f’d here!

But yeah this is all very fine glitter. What I pulled off the magnet feels like a very liquid paste at best. No real “grit” to it

 

Never look at the first oil change you do in a brand new vehicle, you'll likely cringe and wait for it to blow up for the next 50K miles. [and yes, that includes Toyota's] My 15 Taco wasn't too bad at 500 miles but my 14' FJC, O Lord have mercy. [Which is why I always do the first change pretty darn early] Break in wear is real as metal bits burnish and wear in together.

 

I would say based upon the wear pattern, and lack of noise, that you are fine. The glitter is nothing I would be overly concerned about. Diffs run on the dirty side predominantly anyway. I would check it within the next 5000 miles and see what it looks like from there.

 

It's my understanding that most of the 'break in' glitter comes from the machining marks in a new gear set (ring and pinion), wearing in together.
Since you used the same old gears, I don't think you should be seeing all of that.
It may have been left in the diff tubes from the previous failure, but I'd definitely keep an eye on it.

 

Checkout "gold plug". It's a drain plug with a very strong magnet. It can manage that glitter much faster than the stock plug.