Posi. Differential Oil

[Jack H.]

Chester, Next meeting will be Thursday August 19 at Steve Hack's home/shop. Email me if you need directions.

[Dan White]

Posi. Differential Oil

I recently recieved my 66 posi. diff. back from the rebuilders, and am not sure what kind of oil to use. I know I need to use two bottles of additive, as per intructions from the rebuilder, but I am unsure what kind of oil to use. I already have GM 80W-90, but my rebuilder said uses something heavier, can't remember off hand what it was though. Is my oil ok, or should I buy something else, and if so, what? Thanks, Dan

[George R.]

Re: Posi. Differential Oil

Danny, I used GM lubricants, one 4oz. bottle each of "Limited Slip Lube Additive" GM# 1052358.

And two 23oz. bottles each of "Axle Lube SAE 80/90" GM# 1052271.

You need the limited slip oil. Do you know why your builder wanted you to use a heavier oil in the rear end than the factory 80/90?

Good luck,grr#33570

[Duke W.]

Re: Posi. Differential Oil

Use the gear oil and additive mentioned by George. You'll need a sufficient quantity of the 23 oz. gear oil bottles to make the approximate 3.7 pint capacity of the diff.

I'd recommend starting with just one 4 oz. bottle of the additive. If you don't get any chatter, okay. If you do, add a second bottle. The more additive you have the more "slippery" the clutches, so more additive will reduce the limited slip effect. You want just enough additive to keep the clutches from chattering.

Duke

[Chuck S.]

Color Me Cynical...

George,

I expect the rebuilder wanted Dan to use a heavier lubricant because the heavier the lubricant, the less likely he will hear ole Dan bitchin' about his noisy rear end.

Chuck Sangerhausen

[Dan White]

Thanks Guys *NM* *NM*

[George R.]

Re: Check for pinion seal leaks

Danny, after you installed the rear differential and oil let it sit in the air overnight and see it that pinion seal leaks on you.

Mine did right after I installed the differential and hooked up my drive line and put it back down on floor. The next morning I had a leaker. This happens every once in a while. It's my second time in many rebuilds.

Good luck,grr#33570

[Craig S.]

Re: Posi. Differential Oil

Dan - Charley Smith teaches classes in Bloomington on Corvette rear ends and he has built around 7000 rear ends over 35 years, and ships all around the world. He highly recommends using GL6 gear lube (GM's 23 oz bottles are only GL4). He also says to use two bottles of the lube. When I took his class in 98, he said to use Mystic JT7 rated GL6. I bought some from my local differential specialty shop here in Tucson and he also swears by it. It is about the same price as synthetic lube which is ususally GL5, at $4.75 per quart. It is made by Citgo....Craig

[Craig S.]

Re: Posi. Differential Oil - Addendum

I said two bottles of lube - I meant two bottles of GM posi additive. Use the correct amount of lube to fill to the fill hole level....Craig