Rear axle grease

[clazar]

I had my car ( 70 RR ) in for a state inspection. I had the mechanic check the rear axle fluid. It was way low. He added synthetic fluid to top it off, about a full bottle. Will mixing synthetic with normal fluid cause any problems. And I didn't add any sure grip additive.

Chuck

 

[AR67GTX]

Probably not - do you know what was in it to start with? Surprised it was that low. If it makes any unusual noises when turning tight corners the I would add a bottle of limited slip friction modifier. If it's quiet then you are probably good.

 

[burntorng70]

The synthetic fluids that I have used are good for limited slip clutches, say so on the bottle.They also are fully compatible with other lubes.

 

[beanhead]

It shouldn't hurt, that said common wisdom says no synthetic in a clutch-type diff. My shop said the same, don't run it in the sure-grips just use regular with some additive.

 

[clazar]

How much fluid does the rear diff hold ??

Chuck

 

[Fran Blacker]

8.75 2 quarts.

 

[33 IMP]

I had a friend who owned a one-man differential shop, specializing in 9inch, but did anything that came in the shop. He has done 8 3/4s and 9" for me. ( he passed away recently from cancer).
He would warrantee anything with synthetic gear lube for six seconds/ six inches, which ever came first. It was his way of convincing people to use good gear lube. He always used and recommended Torco.

 

[clazar]

It is the 8.75 rear axle. What is the best weight lube to use??

Chuck

 

[33 IMP]

I'm in socal and travel to arizona often. 45* winter, 110* in the summer, my friend recommended the heaviest I could find. I haven't seen 140wt in a while, so i use 85-140. With your winters, I wouldn't recommend that .
I would check with a local race rear end shop for their recommendations.

 

[wyrmrider]

First it's oil not grease
75W-140 GL-5 or better (not for manual trans)
some old additives are no longer used so hard to get dino oil to work anymore
so use Synthetic
much more film strength so takes less EP additives