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PO item #6 (need to start writing these down). [2005 Express 2500]
Checked the diff fluid, finally manage to get the fill plug out with the combo of a breaker bar and a floor jack. Phew! The level was low and best I could determine from Hayes and a ebay-junk-hack FSM was that the level should be at the fill hole, so added a about a pint or two. After starting the engine while still on jacks, I thought about putting it in gear and see how it sounded. Lucky me, decided I better hand rotate the axles first, just to make sure. And right away, the diff locked after half a turn! After a little more dinking with it, pretty clear there's something floating in the diff that's stopping the gears when in the wrong place. So, time to change the diff fluid (PO #6). Now the fun part.
The diff looks like this:
So far, my guess is it's a GM 12 bolt. I think, not familiar with those or identifying outside of an FSM. Problem I'm running into, which seems to be a trend, can't find a 12 bolt cover gasket that would fit. Starting to think maybe the PO replaced the axle.
Am I right? What is this thing?
Really surprised that Hayes and my junk-FSM have little information on diff identification. Heck, the Hayes manual mentions removing the diff cover to service the axles, yet doesn't cover removing/installing the cover! No torque specs or anything! The junk-FSM has plenty of stuff, for a 10.5",9.5" or 8.5" diff ring. Uh, do I have to rip this thing apart to figure out which I have?? Guess I'm spoiled, I get the real FSM for my '87 Corvette on CDROM for $30, all I see for less than $100 for the van is the Hayes or junk-ebay.
FYI, don't buy the $15 ebay special Express FSM unless you like 3000+page PDFs with hacked GM images.
OOPS: Forgot RPO codes might help, haven't found anything that makes sense other than the ratio being 3.73.
FE9 FLT GT4 G80
Last edited by Kael; November 21st, 2019 at 3:56 PM.
Reason: Added RPOs.
If you can't find a gasket, you can always just use RTV gasket maker.
Torque spec isn't critical. Cover bolts don't do anything mechanical or structural, and there shouldn't be any pressure inside. Just make sure they are snug.
GM hasn't made a 12-bolt since '87. Turns out you have a Dana axle that is unique to these vans. It's a Dana 60 with 33 splines and 12 bolt covers (normally 10).
"Dana stamps the ring gear with the part number and the BOM on the axle tube."
"Its a different style Dana 60 that they are using under the Savana/Express vans."
Axlebuilder.com:
"Note: The 33 Spline Dana Super 60 rear axle uses a 12 bolt differential cover that is different from the standard 10 bolt Dana 60 cover"
Also Rockauto has this part: (ACDELCO 88963585 Rear; 9.75 Ring Gear Dana)
It looks like you can use a common 10-bolt gasket and poke two more holes at the top and bottom. The rest look like they line up.
From axlebuilder.com:
"Red High-Temp RTV Silicone (available at your local auto parts store) is the most common way to seal the differential cover on a Dana 60 axle"
Last edited by mountainmanjoe; November 23rd, 2019 at 2:52 PM.
If you've got RPO G80 then it should be the same lube as the vanilla diffs: SAE 75W-90 Synthetic Axle Lubricant (GM Part No. 89021677, in Canada 89021678).
Most likely it will be the Eaton Automatic Locking Differential (ALD A.K.A Gov-Lok), but GM has used others in the past. If you want to be sure, then visually compare the innards of your diff to photos. It is recognizable by the flyweight and pawl mechanism on two shafts, visible from the outside.
November 21st, 2019, 3:51 PM
Which rear axle? Hmmm
