At 1500 miles on the new '05 LLY, I finally got around to changing the rear differential fluid...as per you guys' recommendation.

I was shocked. Oh the humanity! It was the most disgusting pathetic excuse for gear oil I've ever seen. To call it grape juice is an insult to grape juice. You could stomp on red grapes with muddy feet and get cleaner grape juice than this stuff.

To anybody still just considering changing out the factory fill in the rear diff, do not hesitate. I might even do it again after another 500 miles...just to get the last of that garbage out.

And, it does smell like grape juice! Even says "New Grape Scent" on the bottle. I thought it was just a nickname. I'm going to let that sample sit for a couple weeks and see what settles out. Then I'll post more pics.

Thanks to this board, I got that trash out of there...Replaced with 3.1L of new GM fluid. I never would have thought of changing it early. Thanks guys.:thankyou2

No need to do it again in 500 miles. I did my first change around 1500. When I changed it again at 42K it looked like new. Later! Frank

It is good a very good idea to change it out early in the miles. But I really doubt that it was that dirty. The main reason you want to change it out is to get out the metal filings and maybe some large pieces of metal that may have come loose. There should not be any reason for the fluid to get very dirty that early from contamination other than metal pieces.
I may be wrong and others will have a better knowledge of this than me, but there really is not any reason for it to get that dirty except for the metal and over heating. And I really doubt that you burnt up anything in the rear end in that short of time and if so you would be able to smell it.

The black color comes from the locker disks wearing in. Later! Frank

I changed mine factory fluid out a bit late (10000 miles) and when I drained it, it looked fairly good for 10,000 miles of break in.

Dan

dont forget to do the front, you think the rear had alot of junk in it..

I replaced mine the first time at 2600 miles. The rear was filthy but the front was clean as new. I just replaced them again today at 20K miles and both front and rear fluids that came out were like they were new. The front drain plug mag had some crap on it but that was it.

It's been a couple weeks. The grape juice sample has been sitting on my workbench, covered and undisturbed the whole time.

Most of the fluid is still murky, and has not cleared up. There is also now a 1/4" layer of gray sediment in the bottom. That's alot for a 300mL sample. All that crud was once suspended in the fluid.

Thats cheap insurance... an ounce of prevention....