Rear Differential Fluid?

[Nick S]

Simple question. What brand and type of fluid are you using in your rear differential? I am planning on having it changed and am wondering what everyone else uses in their Corvette.

Thanks.

Nick

 

[Vettelt193]

i stick with Mobil 1 if I can... makes life easy


Others use RedLine, some stick with the GM stuff

 

[wx briefer]

Valvoline here, with the GM additive. I used 2 bottles of additive since many profess that to be better for the rear end on the street.

 

[74bigblock]

GM and GM here. Make sure not to switch from regular to synthetic or vice-versa... The seals may leak if you do.

 

[wx briefer]

GM and GM here. Make sure not to switch from regular to synthetic or vice-versa... The seals may leak if you do.

Got proof of that from actual experience? I have changed Harley, '81 Mercedes, '84 Ford, '91 Ford and various small engines over to synthetic with no problems. Actually, experienced less oil leakage in two vehicles!

I keep seeing this 'more leak' stuff professed often, but I think it is propagated more out of ignorance than actual experience.

 

[74bigblock]

Yep... got a '66 in the family that leaked like a cheap diaper. If you have an older rubber seal that has dried out a bit... the synthetic fluid swells the rubber. The cracks in the rubber that formmed from drying out then expand... and they leak.

 

[Hib Halverson]

I use Red Line Heavy Shockproof in the rear axle of the 71 and the 95. I use Red Line 75w90 in the 04, but I'll change that car to RLHSP the next time I change the lube.

The vehicles which will have trouble with seal failure are those built prior to about 1980. Previous to then, some rubber lip seals, like those used on pinion and axle shafts, are not compatible with some components in synthetic lubricants. The solution, of course, is to put new seals in place.

 

[froggy47]

I use Red Line Heavy Shockproof in the rear axle of the 71 and the 95. I use Red Line 75w90 in the 04, but I'll change that car to RLHSP the next time I change the lube.

The vehicles which will have trouble with seal failure are those built prior to about 1980. Previous to then, some rubber lip seals, like those used on pinion and axle shafts, are not compatible with some components in synthetic lubricants. The solution, of course, is to put new seals in place.

Do you add the GM friction modifier to the RLHSP?

 

[74bigblock]

I do yes.

 

[grndspt]

I used Mobil 1 synthetic with a bottle of GM additive!

And I also added a small drain plug to the aluminum case of the rear. (Next time I change the fluid it will be easy to drain).

 

[96CERon]

Mobil 1 synthetic 75w90 with a bottle of GM additive--do you have a picture of where you put the drain?

 

[grndspt]

I have an article on how to install the drain plug. I can scan it but I don't know how to post it. If you want I can email it to you!

 

[WhalePirot]

Lucas Gear Oil 75W90, as recommended by my rear-end shop. The guy is low key and has been building diffys for decades, in all sorts of vehicles. He claims the non-synthetics lube better, while the synthetics have improved heat tolerance. I opted or the syn, solely because the exhaust pipes are right under the diffy and radiate loads of heat.

 

[ßill]

I just put Redline 75w90 in mine with no additive (not recommended by redline). Only have about 500 miles, no problems.

 

[froggy47]

Hi Bill,


Why would you use Redline with NO additive if Redline DOES recommend an additive

I just put Redline 75w90 in mine with no additive (not recommended by redline). Only have about 500 miles, no problems.

 

[ßill]

As coppied from the Red Line web site, and advised by my corvette shop

" 75W90
Our most popular gear oil, this is the preferred product in nearly all car and light truck differentials, both conventional and limited-slip. 75W90 is preferred for most racing applications. It contains friction modifier which is recommended for limited-slip units. 75W90 Gear Oil can be used in many transmissions and transaxles; however, other Red Line lubricants have better frictional properties for rapid synchronization. Exceeds API GL-5."

 

[Roadster Guy]

How do you determine when to change the diff fluid?

Simple question. What brand and type of fluid are you using in your rear differential? I am planning on having it changed and am wondering what everyone else uses in their Corvette.

Thanks.

Nick

Slightly off topic, but, how often do you guys think the rear diff fluid should be changed? And would you measure that interval by age or mileage or both? The 101 Projects for your Corvette (C4) book I think says after 100,000 miles (I don't have the book in front of me so I could be wrong). I think my manual says the diff fluid is good for life, but the manual says that about the ZF too and that is wrong.

I have changed all my other fluids this winter and was wondering about the differential. I have 31,000 miles on the car, but it is 9 years old and original fill. By the way, I think the aftermarket drain plug mentioned earlier is a great idea. Anyone have anything negative to report on those?

 

[Checklst]

I read Bill's as "not recommended by Redline", some synthetic read they have the limited slip additive all ready in the mix. I will say I am getting ready to change my fluid, and the thought of not using the GM bottled additive makes me a little nervous because the cost to my wallet on a goof up would be painful.

 

[catbert]

I've used Redline in all my cars since 1984 when I put it in my first Vette. I've never had transmission or rear end problems. I can't swear it's the Redline, but I'm not taking chances since I do tracktime and AutoX.

 

[WhalePirot]

I used Mobil One in the diffys of my '90 Suburban and in the Vette, until both failed. It was NOT for lack of care or 'beating' either vehicle. In the Vette's case, it was the stock engine. I now follow my expert/rebuilder's advice and use Lucas Gear Oil, which exceeds GL-5.