Differential Fluid

[GrndNatnl]

What weight gear oil should I use in my stock posi rear in the GN? And should I use the pre-mixed gear oil with posi-traction addative already in it? Or just regular fluid, with a tube of Equa-Torque?

And correct me if I'm wrong... The Fel-Pro differential cover gasket number for our rears is: RDS 55072 (?) For 7.5" ring gear, 10 bolt rear.

Thanks in advance. Going to be doing a fluid change out back soon. Believe I have some posi noise. Just wanted to see what weight gear oil some of you are using.

 

[Terbro]

Most of the auto parts stores I've been in only carry one weight gear oil.

As far as the posi additive, after having my rear end rebuilt with Eaton posi, etc, mine begins to moan after about 10k miles. So I now change my fluid and add 2 tubes of posi additive.

Can't comment on the stuff w/posi-additive already in it.

"Posi noise" you will only hear at very low speeds in tight turns. It will sound like moaning, and FEEL like something's grinding or rubbing.

 

[GrndNatnl]

Yup! You hit the nail right on the head! Thats exactly what happens. When I go around a turn/corner just drifting, theres no noise at all.. but if I give it any throttle in the least, I get this "rub.. rub... rub.. rub..." And its NOT a tire. (That was the first thing I checked all around for.)

I also get it at higher RPM just before it shifts into gear (OD). But I think that could be related to my converter.

Someone at work told me 2 tubes (4 oz each) would be too much. On the back of the tube it says only use one tube. Anyone else use 2 without any problems? What COULD happen if over used, if anything?

 

[Renthorin]

Per GMTTYPE.org I run 75w90 lube. I use Mobil 1 syn and you don't need to add the anti chatter stuff, it is already in there (so I was told).

Never hear any noise from the rear.

 

[turboaddict2]

I used the exact fluid you used Ren, except I added a bottle of GM posi additive for good measure. been over 10k miles with no moaning yet

 

[GrndNatnl]

So you can mix the synthetic gear lube with posi addative anyway?

Which parts place usually carr the mobil one lube? I know mine doesnt. Just the Castrol Syntec gear lube. I would prefer the mobil. I'll have to check around.

I may just add a tube of the addative for good measure as well. I'm all about extra measures.

So... 75w-90? Would 85w-140 be too thick?

 

[325DR]

I have heard on this board in a previous post that you shouldnt use the limited slip additive in a drag raced car because it will actually make the rear end "slip" on a hard launch. Any more info on this?

 

[turboaddict2]

75w-90 is fine

 

[Crazi]

I was on the Auburn site and they say change the fluid every 7500 mi. I never knew there was actually an interval and had the same fluid in for ALOT longer then this but changed it twice last year and am changing it again this spring.

I am going to use Lucas Oil stabilizer and half a bottle of Mobil1 I have left over. Anyone see a problem with this? The lucas feels alot slicker then mobil1 and even though the viscosity seems higher, the viscosity index is similar per their websites.

 

[BABY BOEING]

I just rebuilt my rear this winter and used Mobil 1 and a tube of Red Line additive. It sounds good with no chattering or moaning but only got to do a short trip around the block. The weather we have been getting really stinks. You don't want to get the gasket for a 7.5 10 bolt, that's what came in N/A Regals the turbo cars have 8.5 10 bolts. Hope this helps, Jon

 

[GrndNatnl]

Ok.. anyone have the FelPro gasket number for the rear?

 

[MIB]

Felpro Gasket 55028-1.