ewww.... since changing a diff is such a pain in the butt, and changing the oil is both cheap and easy,
me,
I'd change it AGAIN in 2500 miles just to make sure the new stuff comes out clean.

I usually do mine every 50k, and the oil comes out looking just a little darker than it went in.
The transmission's usually pretty dark at 50k, so I try to do it more often. I'm sure it's just
the synchro material, but again, it adds 10 minutes to an oil change and costs $40,
and it makes me feel better.

t

 

Ah, the joys of living in USA with service oils being pretty cheap. The 75W140 was AU$50 and free shipping through Amazon otherwise woulda been closer to AU$70 as even 75W90, or was it 75W85, isn't in all the autoparts stores and certainly not the 75W140. Can get 80W140 in store but not necessarily from a decent brand name.

The ZF auto is over AU$130 to change the fluid in and these days in Oz for a median wage earner that $100 is half the weekly groceries cost so one has to budget for even service items. I only ever buy engine oil when on special cos otherwise that's over AU$120 for 7L.

Anyhoo, not a bad idea to put some coin aside to change it in 4000km to see how it's doing.

 

A good friend of mine was born and raised in Oz (Alice Springs) but now lives in USA. He considered moving to Victoria to be near the parents, but quickly changed his mind after looking into pay scales and living expenses. It was actually much cheaper to stay in USA and fly the whole family to Oz twice per year.

 

Yea, just about to buy a house that should be going for around AU$250-300K but is actually going for just under 3/4 of a million!!!! And then I'm going to struggle seeing my folks in the UK every two years with flights being 1800-2500 each. Which for a current family of 3 makes a holiday an easy $10K and that's with free lodging at my folks. Yet CEO's get paid millions for being useless twats that do far less hours than the actual workers of industry. But I digress................................

 

Wow. I agree with Toby. Change that diff oil again and soon to see if the diff is internally disintegrating. My E46 had no record of the diff oil being changed prior to when I did it at 220,000 miles, and the oil looked fairly clean and definitely did not contain the sort of glitter that you're seeing! I sort of suspect that a new diff is in your future, but if it's quieter and is working for now, there is no harm in hoping for the best!

 

I see sludge. I probably do it sooner than 2500 miles. In fact, I would be tempted to drain and fill first with ATF, roll around the block and drain the ATF. ATF is great is getting grim and sludge out. OTOH, like others have eluded to, the sludge may be what's holding your diff together.

 

that’s pretty dark for not being a LSD. i would like to see how it would’ve looked with RedLine synthetic oil vs that cheaper Nulon oil you used. and did you say you had “additive” added to the prior diff oil change or just this one? lastly is the drained oil in photo also the residue oil and grime from spraying it clean in same pan?

 

That is just the oil and additive that came out. The Nulon oil was golden and the additive gray so a mixture of the additive and remnants of the old black oil making the Nulon turn black me thinks. The additive seems to float on top of the oil like a film of aerated lighter gray schmuz.

I had been wondering if I'd need another diff but shall see how we go with the new oil in there. I mean it has run for 3 years after I drained the factory oil and did make things quieter. Getting hold of a 3.91 will not be fun in this wonderous country I live in.

With the cover off the crown looked pretty nice with just regular wear of the case hardening so I'll keep me fingers crossed.

Gotta do the front bushes as I still get a slight thunk from the diff going between drive and reverse and when change the rear bush I could see the diff sitting much more towards the bottom of the bushes than it should but hey, they are 25 year old bushings.

 

ah, I can smell it from here