View Full Version : Changing rear diff fluid


WannaZ28
09-25-2006, 09:41 AM
Got a 95 TA, its clocking in at 121k miles and i want to change the rear fluid. since ive never done this before, does anyone have a link on how to change it like (similar to changing the window motor and headlamp gear i found on this site). any suggestions on the rear diff fluid i should use?

Revelation Z28
09-25-2006, 10:10 AM
unbolt all 10 bolts on the cover, put a pan underneath, and pry the bottom slowly with a screwdriver and let it sludge out until it slows down then take the cover off. scrape the gasket off of the housing and cover mating areas with a box cutter or surface cleaner or sand paper. put RTV sealent around the 10 bolt holes on the housing and put the gasket on aligned to the holes. put RTV around the cover bolt holes and put the cover on. then tighten all the bolts up. fill with gear oil/limited slip additive until its level at the bottom of the fill plug.

hope that helps.

irnbru83
09-25-2006, 11:55 AM
please remember that if you put RTV all over the place, it is going to be incredibly difficult to get back in if you need to. We have stuff at work to dissolve the RTV, but it is still a pain ;p

TurboZ28
09-25-2006, 12:48 PM
Make sure you use GM brand limited slip additive, not the stuff from Autozone. Not sure why but everyone says go to the dealer to get the stuff.

todddchi
09-25-2006, 01:13 PM
1.) I've always used a GM paper gasket and zero RTV. Through 3 different 10 bolts on 2 different cars spanning over 120k miles, I've never had a single gasket leak, not even a seep. It is my opinion that very meticulous cleaning of each mating surface is more important than anything - it can take a good bit of elbow grease to get all of the old gasket and rust cleaned off. I recommend using a brass wire brush and steel wool as opposed to sandpaper to minimize roughing of the surface and loss of media into the diff. Also be sure to uniformly tighten the bolts in a criss cross pattern.

If you decide to use RTV realize that most of it needs at least a couple hours before fully setting, and it should be allowed to do so before you add oil.

2.) Take note of the brake line bracket locations, the bolts used in those holes are longer.

3.) Be very thorough in your cleaning of the rear cover and the magnet. A lot of material will get gummed up around the magnet that won't come off unless you get in there and scrub, hot water alone won't cut it.

4.) I agree to use GM LS additive, may as well get that and the gasket at the same time while at the dealer. They tend to have them in stock, so if you have several dealers by you call and find the cheapest one.

5.) The fill plug is located just high enough that getting normal diff oil bottles emptied in there is a pita. You have to kind of wedge the bottle in there horizontally and pump the back half. You'll use about 1.7 jugs, when it runs out on it's own you are full.

Caswell
09-25-2006, 01:18 PM
I'd agree about the gaskets w/o RTV. When I changed mine I didn't use any RTV, and it's been bone dry for 35K miles. Probably time to change it again.

Glad someone else thought it was a PITA to fill it back up. I think I ended up putting a piece of clear tubing over the spout on the Mobil 1 bottle and squeezing it out.

todddchi
09-25-2006, 01:36 PM
I've found if you kink the bottle at the midway point, you can wedge it up just right to keep the top half level and use the back half to pump most all of it in. You have to kink the sheet out of the bottle though.

The tube would work great, but I don't think that far ahead. :P

SLO98Z
09-25-2006, 02:55 PM
Autozone has the perfect thing for about 3-4 bucks. Its screws on to gear oil bottles and has about 1 1/2 feet of clear tubing and a shutoff valve. It's the best thing I've found yet.

mcamp001
09-25-2006, 07:53 PM
Autozone has the perfect thing for about 3-4 bucks. Its screws on to gear oil bottles and has about 1 1/2 feet of clear tubing and a shutoff valve. It's the best thing I've found yet.

Amsoil has a great one, although Amsoil bottles have a wider mouth, and it is designed for them. What I like is it's an ounce a pump, that is one pump will draw one ounce of fluid, so 12 pumps = empty quart

Da Swami
09-25-2006, 11:13 PM
Do you really have to pop off the cover to drain the fluid?

I thought you could suck it out with a pump through the fill hole....

Revelation Z28
09-26-2006, 01:03 AM
not if you want to check for metal shavings or wear on the gears.

Do you really have to pop off the cover to drain the fluid?

I thought you could suck it out with a pump through the fill hole....

WannaZ28
09-26-2006, 06:13 AM
does the procedure below still apply? how long would it take a handy noob to handle this?


unbolt all 10 bolts on the cover, put a pan underneath, and pry the bottom slowly with a screwdriver and let it sludge out until it slows down then take the cover off. scrape the gasket off of the housing and cover mating areas with a box cutter or surface cleaner or sand paper. put RTV sealent around the 10 bolt holes on the housing and put the gasket on aligned to the holes. put RTV around the cover bolt holes and put the cover on. then tighten all the bolts up. fill with gear oil/limited slip additive until its level at the bottom of the fill plug.

hope that helps.

WADDISME
09-26-2006, 08:41 AM
So Amsoil has 12 oz per quart :confused:

todddchi
09-26-2006, 02:23 PM
You can do use a pump exchanger to do a fluid change, but it won't do as much good. A lot of the benefit you'll get from doing a full change is getting into the diff to clean all the shavings off the magnet, wipe the gunk that has accumulated at the bottom, and scoop out all the fluid you possibly can.

Using a the hose method would miss probably 20% of the fluid you'd get taking the cover off. Most quick lube places just do a vacuum change like you this. It is better than nothing, but it is much preferred to remove the cover and clean things up.

I would say this goes doubly for guys with Auburn diffs that have remnants from the clutches wearing.

Do you really have to pop off the cover to drain the fluid?

I thought you could suck it out with a pump through the fill hole....