help replacing fluid in rear end

[Brocks GN]

I have noticed there is a small leak comming out of the diff. cover at the bottom. I want to take it off and replace the fluid... Never messed with a rear end before. How do you go about it and what fluid would you recommend using?

 

[Red Regal T]

First locate a new gasket. Just take off the bolts and drain the rear. Advance or Auto zone will carry gear oil for your rear and you squeeze it in, or attach a rubber hose to the nozzle and squeeze in the gear oil. You'll need close to two quarts. The fill in on the side of the rear. Fill until it's running back out of the hole. The fill plug takes a square 3/8" drive to remove it. Sometimes after not being off for years, they are tough to get off. Do your best not to damage or round out the 3/8" cavity of the plug.

 

[Blown&Injected]

Very easy; just dirty and stinks, don't know WTH is up with the smell of gear oil.

1) Get new gasket for 8.5" 10 bolt rear
2) Put pan under rear
3) Take the cover off
4) Clean cover and bolts
5) Install cover with new gasket
6) Find fill hole - it is about 2/3 high on the rear in the side - it has a set type screw about 3/4" with a 3/8" square female head - use a ratchet with a short extension and just put the end of the 3/8" drive extension into the plug to remove and replace it.
7) Refill with what ever you want + a bottle of the GM Limited Slip additive - some say 2 bottles, but then there is lots of ideas on what else to use in the rear. I have always used 80w90 gear oil and one bottle. There are plenty of gear oils, do a search for ideas. The real hard part is getting the oil to the fill the rear. Just squeeze the stuff in until it starts leaking back out the plug. A piece of hose on the end of the bottle helps.

 

[Blown&Injected]

I'm a s-l-o-w typer

 

[tom h]

Also:

spread non-hardening sealant (eg, Permatex #2 or Hylomar) on the new gasket.
New gasket: GM # 26016662.
apply a bit of anti-seize to the bolts.
tighten the diff cover in a gradual criss-cross pattern, like a wheel.
torque to 20 ft-lbs.

GM gear oil spec is 80W-90 / GL5.
if using regular hydrocarbon gear oil, also add 1 tube of GM #1052358 Limited slip additive.

 

[turbo nasty]

You are going to need a gasket for a GM 8.5 10 bolt rear cover you can get that at the parts stores.

Jack up car level (needs to be close to level) and secure, remove the fill plug from rear end housing using 3/8 drive ratchet (i think) might need a short extension (fill plug is up high on the pass side of the chunk on the front), once plug is out get a drain pan under the rear end.

Remove the bolts on the rear cover so that the cover can open up at the bottom some and not fall off.
If it falls off the fluid will just fly out when the cover comes off and go everywhere. You want the bottom open only for a controlled drain.

You might have to give the cover some help to come loose (medium flathead screwdriver, be careful not to bend the covers mating surfaces).

Once drained scrape off all the old gasket if it stuck anywhere.

Get a few rags and wipe the bottom of the chunk to keep the lube from oozing out at the bottom make sure beacause face of rear housing where the gasket goes needs to be oil free for the next steps.

Get some brake clean on a clean rag(s) and clean (clean very good) both mating surfaces (cover and rear housing where the gasket is going to lay.

Once clean get some ultra copper high temp gasket maker (permatex brand) and apply to mating surfaces (cover and housing) careful not to get a super thick coat, a 1/16" coat all around is all that is needed.

Align and place gasket on cover, then use a few bolts around the top through the cover holding the gasket in place (stick one bolt in 2 oclock pos and 1 in the 10 oclock to hold the gasket) while starting the bolts...now start the others by hand.

Tighten bolts up tight but dont rupture the gasket and distort the cover with the jungle grip.
Once cover is back on and secure u can refill the rearend through the plug you removed with the 3/8 ratchet.

I bought a hand pump at the parts store (by the gear oils) as it is a heck of alot easier than trying to use a hose hooked to the end of the bottle and hand squeezing it.
My cocktail of choice is the below, this mix has works for tens of thousands of miles trouble free and keeps the chatter away.

1 bottle of Lucas Oil Stabilizer (dino)
1 bottle of Valvoline (dino NOT SYN) 75w90 Gear oil
1 Tube/bottle of Limited slip additive

Put the lucas in first then the limited slip additive and top off with the 75 w90 until fluid just starts to come out of the fill port and then replace the plug and tighten, clean up and you are done.

You can get rear end covers that have a drain plug in them or get a kit and put one in your stock cover so you do not need to remove the cover for future lube services.

I typed this super quick so not sure if it is grammar correct but will help if nothing else...good luck

 

[Red Regal T]

I'm a s-l-o-w typer

:biggrin:

 

[Brocks GN]

hey thanks guys. sounds pretty straight forward i'll be getting dirty and smelly today . Thanks