How to change rear differential fluid.

c schoelen · Post by **c schoelen** » Sun Jan 01, 2006 2:52 pm

does anyone know how to change the gear oil in the rear axle?

Post by **HenryJ** » Sun Jan 01, 2006 3:05 pm

Removal of the rear cover is required.
Many have taken that opportunity to upgrade the rear cover to one that includes a fill and drain plug. A truss cover is a good idea too , since the 7.5 and 7.625 rears are reported to be a little flexy.

If you're not "into" changing covers, just remove yours to drain the oil. Clean it up and use a bead of good RTV to seal it during assembly.

c schoelen · Post by **c schoelen** » Mon Jan 02, 2006 8:15 am

how do i fill the fluid back up after i have taken the cover off?

Post by **HenryJ** » Mon Jan 02, 2006 8:18 am

There is a threaded plug on the front side of the differential. Use a 3/8" drive extension to remove it. Then fill to the bottom of that hole. (after re-installation of the cover.)

GM Data wrote:Front and Rear Axle Standard Differential Axle Lubricant (GM P/N 1052271) or SAE 80W-90 GL-5 Gear Lubricant

Rear Axle (Locking, Differential) Axle Lubricant, use only GM Part No. 12345977 (in Canada use Part No. 10953482). Do Not add friction modifier

The owners manual lists: Front and Rear Axle (Standard Differential) SAE 80W-90 Axle Lubricant (GM Part No. 1052271 or equivalent) and Rear Axle (Locking, Differential) Axle Lubricant; use only GM Part No. 1052271 Do Not add friction modifier

jeff024 · Post by **jeff024** » Mon Jan 02, 2006 11:32 am

with your truck having the SL you shouldnt even need to jack it to get to everything

Steve2003 · Post by **Steve2003** » Mon Jan 02, 2006 1:40 pm

jeff024 wrote:with your truck having the SL you shouldnt even need to jack it to get to everything

maybe not but I still drive my truck up on ramps to change the oil! The more elbow room the better

Steve

jeff024 · Post by **jeff024** » Mon Jan 02, 2006 1:46 pm

I dont even put mine up to change the oil

michael_4x4 · Post by **michael_4x4** » Tue May 09, 2006 9:47 am

How often should the fluid in the rear diff be changed....and what else is some more good maintance to do?

jeff024 · Post by **jeff024** » Tue May 09, 2006 11:31 am

dont forget to grease your fittings/

rick · Post by **rick** » Tue May 09, 2006 11:34 am

Don't forget that if its a Posi to put Posi fluid back in.

Post by **HenryJ** » Tue May 09, 2006 1:29 pm

rick wrote:Don't forget that if its a Posi to put Posi fluid back in.

Nope. The G80 does not use a friction modifier.

GM Data wrote: wrote: Front and Rear Axle Standard Differential Axle Lubricant (GM P/N 1052271) or SAE 80W-90 GL-5 Gear Lubricant

Rear Axle (Locking, Differential) Axle Lubricant, use only GM Part No. 12345977 (in Canada use Part No. 10953482). Do Not add friction modifier

Snoman002 · Post by **Snoman002** » Tue May 09, 2006 5:30 pm

OR, instead of pulling the cover you could get a $10 suction gun and suck the fluid out the fill hole. Won't get ALL the fluid that way but if the fluid is in good shape (read: proper change sequence) then it should be fine.

Do the CC's use the 7.6" rear? I figured they would all have the 8.5".

Post by **HenryJ** » Tue May 09, 2006 7:00 pm

Snoman002 wrote:OR, instead of pulling the cover you could get a $10 suction gun and suck the fluid out the fill hole. Won't get ALL the fluid that way but if the fluid is in good shape (read: proper change sequence) then it should be fine.

Do the CC's use the 7.6" rear? I figured they would all have the 8.5".

It is really tough to get a suction gun to drain the rear differential do the the fill plugs location beside the pinion. That does work pretty good for a front differential though.

I like to inspect the oil when changing. I used to like checking the gear wear as well, but upgraded to a cover with fill and drain plugs, so I don't get to do that anymore. I will pull the cover if I see debris in the oil though.

The CC's all got the 7.6

Blackmobile · Post by **Blackmobile** » Wed May 10, 2006 2:55 am

upgraded to a cover with fill and drain plugs...

Where'd you get the upgraded cover, part no. , price ? At what mileage/age did you change the fluid? I will have my truck for three yrs. in July, but have kept the mileage down (25,000).

Post by **HenryJ** » Wed May 10, 2006 3:46 am

Differential rear-end support cover

The first change for a truck with the G80 should have been at the first engine oil change (3000mi) Thereafter as conditions permit. Every 15-25k mi. is what I try to do. I do check the level/condition every oil change and will change it if contamination is present.

Snoman002 · Post by **Snoman002** » Thu May 11, 2006 4:20 pm

HenryJ wrote:
Snoman002 wrote:OR, instead of pulling the cover you could get a $10 suction gun and suck the fluid out the fill hole. Won't get ALL the fluid that way but if the fluid is in good shape (read: proper change sequence) then it should be fine.

Do the CC's use the 7.6" rear? I figured they would all have the 8.5".
It is really tough to get a suction gun to drain the rear differential do the the fill plugs location beside the pinion. That does work pretty good for a front differential though.

I like to inspect the oil when changing. I used to like checking the gear wear as well, but upgraded to a cover with fill and drain plugs, so I don't get to do that anymore. I will pull the cover if I see debris in the oil though.

The CC's all got the 7.6

True, but I have been able to get nearly all the fluid out of mine that way. Granted, pulling the cover and inspecting the gears will always be better. The main reason I did mine that way was because I busted one of the cover bolts and the jimmy rig I did to stop the leak makes changing the cover a PITA.

I'm supprised the CC's got the 7.6, I figured with the extra weight they would use the 8.5, that and I thought most of the newer 4.3 S_Series trucks got the 8.5 anyways.

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How to change rear differential fluid.

How to change rear differential fluid.

How often?