Gentlemen, Thank you for viewing my post. I am about to lower my '86 AT Corvette and would like to change the rear differential fluid as well. What options do I have to just change the fluid, or flush the diff with oil and a new gasket? I already have the gear oil and gasket, how much of the limited slip additive do I need? I have an 8oz. container, but I think I need 16oz. Any help is greatly apprecited. Thanks!

 

i think you mean dana 36..

it holds just under 2 quarts. i know to change the fluid in my d44 you must remove the batwing. i think the d36 is the same.

when i changed my gears i added just regular 80-90 gear oil in for break in then 200 mile changed to amsoil 75-90 syn and 4oz of l/s add.
you can use silicone for your gasket.. i use permatex ultra black.

 

gee... no... get a hand pump and suck it out.

The mighty-mite is an excellent tool for pumping the old out and the new in.

Also, use 2 bottles of diff additive.

 

bogus, the only reason i took mine batwing off was because i had a seal leak.

 

How difficult is it to remove the rear differential cover? I believe some removal of some suspension pieces is required. Is this true?

 

not to bad.. the spring is the biggest p.i.t.a. it took me a few hours. but had to to change the leaking seal..

bogus's idea is the way to go..

 

OK, my seals and gaskets are good so I'll proceed to suck it out and fill it up. Is 4oz of additive the official quantity need? Thanks again guys!

 

2, 4oz bottles of additive, per Gordon Killebrew.

mos90 - didn't realize you had a leak...

 

8 ounces it is guys. Once again, thank you for all of your time!

 

Not to chide Bogus but, many people believe that 2 bottles is too much... Let's see what others have to say about it. I was promoting more myself a couple years back and got hammered at the time... I recovered though!!!

 

What I did when I upgraded gears, was I drilled and tapped the cover for a drain plug. Even if there is still alittle oil left in the bottom (of the diff) it's much easier to suck out than the whole 2 quarts. Only GM could build a differential (w/limited slip) with a factory recommended oil change interval of 7500 miles and not give you a drain plug!

 

I'm thinking 4 oz is correct. I will call Chevy and post the answer momentarily.

 

According to AMSOILs online database (which comes from a clearing house of info from all manufacturers):

"Models with limited slip use 4 oz of GM part no. 1052358 additive or equivalent when fluid is changed."

 

I Had My Fluid Changed To Synthetic They Put One Bottle Slip Additive In And It Made Noise... They Put Another In And It Was Fine....

 

My experience was one bottle still caused the diff to chatter in tight turns. Two bottles solved the problem..

 

Interesting fact on the milage for fluid changes. Where did that come from? I was just reading my owners manual (89) last night and it said differential fluid did not require servicing. I was looking it up because I want to change mine too. I know a 17 year old car with 100,000 on it HAS to have the fluid changed!

 

It is advisable to run the car for about 10 minutes to warm up the gear oil so it flows better.... BUT watch our for the hot exhaust. the forearm scar is still there and it has been 6 months...It is a tight fit inside the housing. The standard sized tubing on the suction gun(3/8?) would not fit between the spline of the gears so the fluid could not be removed.. Downsizing the tubing to 1/4 inch worked and allowed all the old gear oil to be removed..

Used 2 bottles of GM additive ( Add it first) and then filled the balance with Mobil 1 75W90.
NO chatter, No whine.... just grins.

 

That came from my 1986 factory service manual. The 7500 mile interval comes into play with any GM vehicle with a limited slip (ALL C4 Vettes )

 

Albeit for a slightly different rear,

We used the Mobil 1 on our 94 LT1 D44 with 94k miles almost 2 years ago with no resultant leaks.

Synthetic is better, check the racing circuit, based on what I've read, it's pretty much all they will use.

However, when I did ours, instead of opening-up the differential I used a trick borrowed from the boating world -- suck it out through the fill/level hole instead.

I rigged-up a small shop vac with a plastic bag liner, and a tub of butter container with a large hole cut in the lid set inside the shop-vac (next time will use a Folgers plastic container as it's stiffer).

Through the vacume hose hole I ran a small diameter clear tube, long enough to run from the inside of the butter container, taped to the container lid (but left enought of an opening for the vacume pressure to work through the tube), through the vacume hose and/or inlet and then underneath the car and into the differential.

Then I sucked-out all the fluid I could, added back in about 1 pint as a flush agent (using one of those pumps available for the gear oil containers), sucked it back out with the vacume rig.

Then I pre-mixed the limited-slip additive in the gear oil container and pumped it and the rest of the needed quantity of fluid into the differential.

All this without a lift (just jackstands) and without having to open-up the differential and worry about subsequent leaks.

Hope this helps...

P.S. I copied this from one of my earlier posts talking about which oil to use, the link for which is as follows:

older thread