# Rear end fluid Q



## Cobra126 (Sep 24, 2009)

I havn't purchased a shop manual yet and was wondering if there is a drain plug on our rear ends...... not trying to be funny  I hope there is, and its not the type where you need to remove the whole cover. Also will be using amsoil Diff fluid. No need to mix in any additive as with the GM stuff. Anyone know what fluid I will need off hand?

Thanks!

Well so much for using Amsoil fluid, did a look up and they dont have anything recommended for the GTO rear end  DID say: Differential, Rear......GL-5*
ALL TEMPS......75W-140 [3]
No AMSOIL Product Recommendation


----------



## jpalamar (Jul 22, 2008)

There is an AMSOIL for our rear diff. Not sure what it is but I've heard people using it.

I used Royal Purple because it has the modifier in it alreay and was able to find it in a local store. It was 75Q-140.

Yes, there is a drain as well as a fill plug for our rears. You still may need a syphen or so though.


----------



## Cobra126 (Sep 24, 2009)

jpalamar said:


> There is an AMSOIL for our rear diff. Not sure what it is but I've heard people using it.
> 
> I used Royal Purple because it has the modifier in it alreay and was able to find it in a local store. It was 75Q-140.
> 
> Yes, there is a drain as well as a fill plug for our rears. You still may need a syphen or so though.


 Excellent!! Thanks j! Do you mean a syphon to put the fluid back in? I have a hand pump I use for this. Got it from amsoil for like $10! Screws onto the top of the container and come with the diff size hoses.


----------



## jpalamar (Jul 22, 2008)

Cobra126 said:


> Excellent!! Thanks j! Do you mean a syphon to put the fluid back in? I have a hand pump I use for this. Got it from amsoil for like $10! Screws onto the top of the container and come with the diff size hoses.


I used the Syphon just to get the fluid back in. Easier then fighting gravity. Should drain mostly on its own. Beware though, gear oils usually smell horrible.


----------



## Cobra126 (Sep 24, 2009)

jpalamar said:


> I used the Syphon just to get the fluid back in. Easier then fighting gravity. Should drain mostly on its own. Beware though, gear oils usually smell horrible.


 Oh yes, I DO remember that smell! Thanks for the info!!


----------



## GM4life (Mar 18, 2007)

Cobra126 said:


> I havn't purchased a shop manual yet and was wondering if there is a drain plug on our rear ends...... not trying to be funny  I hope there is, and its not the type where you need to remove the whole cover. Also will be using amsoil Diff fluid. No need to mix in any additive as with the GM stuff. Anyone know what fluid I will need off hand?
> 
> Thanks!
> 
> ...


Yes there is a drain plug for our diffs it is the bottom most bolt on the cover. The fill is the largest bolt on the cover w/a tag attached to it. Our diff require 75W-140 with 1oz of limited slip additive unless the fluid does not require any. I used Royal Purple before in my old diff it didn't require LS additive. I was able to service it without any pumps just tipped the bottle and squirted it in.


----------



## FastFrank (Jun 12, 2009)

I was under the impression that the Amsoil fluid did require the friction modifier additive. At least that is what was recommended to me by Amsoil.

After checking the website just now, it says that Amsoil does not have a product for our rear diffs. They recommend to use the GM stuff - "Use GM part no. 89021809 Axle lubricant 75W-140.
Plus 1 ounce of friction modifier 7098 GM part no.89021958 or equivalent"

Here is a link...

AMSOIL Online Product Application Guide - 2004%7cPONTIAC%7cGTO%7cG


----------



## CChase (Dec 11, 2007)

FastFrank said:


> I was under the impression that the Amsoil fluid did require the friction modifier additive. At least that is what was recommended to me by Amsoil.
> 
> After checking the website just now, it says that Amsoil does not have a product for our rear diffs. They recommend to use the GM stuff - "Use GM part no. 89021809 Axle lubricant 75W-140.
> Plus 1 ounce of friction modifier 7098 GM part no.89021958 or equivalent"
> ...


Unfortunately the problem is that the 89021958 is discontinued.


----------



## jpalamar (Jul 22, 2008)

CChase said:


> Unfortunately the problem is that the 89021958 is discontinued.


There is a replacement part number for the stock rear diff fluid. Call Gene at GM Parts House. He knows the part number and can get you a good deal on it. The FM is already in the fluid now.


----------



## CChase (Dec 11, 2007)

jpalamar said:


> There is a replacement part number for the stock rear diff fluid. Call Gene at GM Parts House. He knows the part number and can get you a good deal on it. The FM is already in the fluid now.


I actually picked up 2 quarts of the new "fluid with modifier in it" which is P/N 88862624, ran me ~$20/qt. This has come up so much in conversation over the past 2 days, I know it off the top of my head. I'd have used Gene except that I only have a window of about 2 or 3 days of warm weather when I'll want to be under the car draining the transmission fluid and rear end fluid I needed instant gratification. If only I could find some kind of synthetic Dexron-III nearby.


----------



## Cobra126 (Sep 24, 2009)

When refilling, am I going to the bottom of the fill hole?, or is there a premeasured amout I need to use?


----------



## jpalamar (Jul 22, 2008)

Cobra126 said:


> When refilling, am I going to the bottom of the fill hole?, or is there a premeasured amout I need to use?


Just fill until it oozes out. Then your done' Should be about 1.5 quearts though.


----------

