NightStalker

I am preparing to change the fluid in my 1969 Cutlass, which has a 12-bolt positrack rear-end.

What fluid should I use when I replace the rear diff cover with a new gasket, and how much fluid will I need?

Thanks,

NS

rcorrigan5

The '69 Chassis Service Manual (page 4B-36), says to use special lubricant number 1050081 or equivalent for your anti-spin differential. I'd check with your local GM dealership to make sure you have the right stuff - they might unsuspectedly sell you the wrong fluid at an auto parts store. As well, if you have a type "O" differential, it should hold approximately 3 3/4 pints. If you have a type "C" differential, it should hold about 4 1/2 pints, according to the book.

Randy C.

Rickman48

There was an additive with 'whale oil' in it, that was the best, but discontinued in the mid '70's! If you could find some, it's added to regular RE 90w oil.
I've seen articles that say Red Line fluid is the best, and is synthetic, but I'm sure others will chime in.

71 Cutlass

I got my fluid from a local GM dealer (Chevrolet) at the parts counter. Just let them know you need the limited slip fluid. (pause)... Just returned from the garage and found the old bottle from the GM dealership, it says: Axle lubricant SAE 80W-90
part # is 1052271. Then below that says Gr.8.800. Been using it in my car for the last 7 years.

NightStalker

Thanks for the advice fella's.

Looks like I'll be headed down to the GM Dealer on Monday.

Rcorrigan: Can I tell the difference between the two rear-ends without opening it up?

NS

Chesrown 67 OAI

check with 507Olds. Brian can tell you the pros and cons of all posi lubes on the market. There are some good ones out there! All of the guys in the know tell us to stay away from the synthetic stuff in the old posi units! Maybe Brian will chime in.
Actually there is much discussion elsewhere on this forum on the subject. Just a few weeks ago Brian had a few good recommendations on the subject! Do a search.

arodenhiser

I am no expert but after looking around to i.d. mine...

Here the top pic is a Chevy type and bottom is a Olds type.



The upside down "V" pattern is easy to spot compared to searching for stamps and numbers. If your car happens to be Canadian built chances are you have the C type.

Adam

rcorrigan5

Arodenhiser has your answer better than I could say it!

Randy C.

alek72us

i thought the olds type "o" didnt have a postrac. am i wrong?

Indy_68_S

Yes & No....Olds had 'Anti-Spin' ...and it was available in Type 'O' rearends...

I have a '68 type 'O' 3.42 Anti-Spin (672 carrier/ 31 spline axles) in mine....

rcorrigan5

...and my '68 4-4-2 came from the factory with (and still has) an "O" type anti-spin 3.08 rear end.

Randy C.