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. 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. 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. 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!!

I would guess that the spider gears are chipped and small pieces are in the case.You could try changing lubricant and watch for parts in drain pan, but if they are damaged it won't do any good.

Servicing a diff is super easy so I suggest you do it yourself. Drain the fluid into a pan and check the bottom of it for metal. If you find anything like this:Then you have trouble and you should get it into a shop for repair NOW. If you keep driving it like that, the bits of metal will go through the gears and eventually destroy them - which will cost you another $600~$750 beyond what the rebuild costs.BTW, those bits are from my spider gears and while you'd think they were just common metal, they must be gold because there's $2300 worth of that stuff there :(

Check the build plate normally in glove box for build data and see if your rig came with limited slip differentials.

well, when servicing my rear diff, should I put back in the 75w90 full synthetic? and with or without the additive?

what am I specifically looking for on the build plate to find out about the limited slip diff?

Another thread on rear diff. lubricant..... | Good Sam Community

Sport45
Explorer II
Dec 17, 2014
jbres wrote:
so is it even possible then to overfill these things?

Yes, you can. There is a fill level specification for a reason. I don't know what that reason is on any particular differential. Overfilling may lead to foaming, reduced seal life, or something else. In some diffs it may cause no problems at all. I'm just not going to be the Beta tester for overfilling.

Too bad there's not a standard that requires the fill port to be put at the proper service level on all of them.
hawkeye-08
Explorer III
Dec 17, 2014
I have been told that Amsoil website is good for checking capacities. I have not used it myself but will when I need to change my fluids.

I just looked mine up here... http://www.amsoil.com/mygarage/VehicleLookupPage.aspx?FromIndex=1&url2=2011+GMC%20TRUCKS+SIERRA%202500%20HD%20PICKUP+D

Differential, 9.25 RingGear Front..........3.6 pints
Differential, 10.5 RingGear Rear..........5.5 pints
Differential, 11.5 RingGear Rear..........6.3 pints
Thunderbolt
Explorer
Dec 16, 2014
Is it clunking when going in a straight line or only when turning ? If it is only when turning the clutches could be glazed. Not sure about the 1/2 tons, but there is a procedure straight from Eaton for the 3/4 tons.
The 1/2 tons have clutch material on the clutch plates and the 3/4 tons are all metal so it may be a different procedure. If it were me I would call Eaton and exolain what it is doing and see what they say.
enblethen
Nomad
Dec 16, 2014
I would fill to just below the fill port.
As long as the vent is clear, I doubt whether any problems would arise. If vent is clogged you could blow out wheel seals.
jbres
Explorer
Dec 16, 2014
so is it even possible then to overfill these things?
Dave_H_M
Explorer II
Dec 16, 2014
Since I drive a Ford, I don't have a clue on your capacity.

Way I do it is fill it until you can just touch the oil with the tip of your pinky by sticking it in the hole and bending it down at the first joint. Personally I am not satisfied with that and have the oil level set at the quick of the pinky finger nail.

Now how is that for being scientific?
jbres
Explorer
Dec 16, 2014
So does anyone know the capacities of these rear differentials? or do you just fill it until it spills out. Seems the dealer, and the local auto parts store has no clue
jbres
Explorer
Dec 15, 2014
well all was fine and dandy, found no metal shavings.. only issue I have now, is where can I find a link for rear axle gear oil capacities? I put in 2.5 qts, as my manual just states fill it until 5/8" to 1 5/8" from top of the filler plug..well after 2.5 qts, I am still about 1.5" inches from the filler plug, but its vary hard to even tell checking it will a bent screwdriver. SO does anyonw know of links to check this? auto zone thinks 1.5 quarts, but that little amount puts it nowhere near filler plug. hmmm
Passin_Thru
Explorer
Dec 14, 2014
We have always run and always will Lucas in our differentials and axles. It has worked flawlessly and brings the temp down considerably in the desert at 120 degree OAT. Beats 90 WT.
beergardens
Explorer
Dec 13, 2014
Sounds to me like a hard-part failure inside the differential that is probably completely unrelated to the work that was previously done. The G80 differential is not a real locker; it has clutches that are only engaged when there is a difference in speed between the rear wheels. Therefore, it requires no friction modifier to smooth out the slippage action of the discs. Clunking and banging don't sound to me like clutch issues. I wouldn't entertain any thoughts of suing anybody until I'd looked inside and seen evidence of something left loose or assembled incorrectly during the previous repair.