Another thread on rear diff. lubricant.....

jbres wrote:
I didn't want to hack the other thread going on with rear diff. questions, but it influenced me to post my issue with my rear diff.
I have a 2003 Chevrolet Tahoe, 5.3 4x4 133,000 miles. About two years ago, I had some work done at local shop on my Tahoe as my emergency brake was really screwed up, and they ended up having to drain the rear diff. fluid.

Ah, GMT800 half ton had rear disc brakes and that silly, tiny drum shoe
inside the disc hub

Many had the sheetmetal bracket inside come apart to mess up and have
to have it hammered to even torched off in order to fix

Others used the now 'Parking' brake while moving thinking it is still
an Emergency brake...to have the tiny shoe wedge itself onto the drum

Another hammer it off or some have to be torched off

A holding plate was screwed up on my e-brake, which was connected with the rear axle. 6 months or so passes, no issues.
THEN, the rear end banging, clunking, chattering, bumping began, especially during deceleration.

Diff's making that kind of noise has something in there or something
has come part

Wonder if they even put fluid back in there

Check your glove box label for RPO code G80, that is a locker diff
and think that is what you have and the clutches have gone without
lube or wrong kind of lube.

No diff fluid modifier is needed

I tried talking to the local shop who fixed the e-brake, and them damn fools could hardly tell me what type of fluid was even used.
So after talking with the local Chevy Dealer, they said try adding a anti-slip. That's what I did, and it still makes the same damn clunking, chattering etc. and its been another year.

If you have the G80, then the dealer did something wrong by adding
the friction modifier

GMT800's had the 'grape juice' diff fluid and think an attempt to
make sure it is synthetic and NO friction modifier

SO, what should I even do?? All my manual states is use 75w90 synthetic axle lubricant. Should I trying changing it again, and make sure I put in the 75w 90 synthetic, because honestly, who even knows what the repair shop ever used!!

At this point, think a complete rebuild by a shop who knows what the
heck they are doing.

Try 4x4 shops, they do many more than dealers ever do. Plus dealers
typically have a high turn over in their service department