old greybeard

Just bought a 69 Cutlass. 350 4b, Canadian built. Trying to determine ratio and if limited slip, want to change fluid with correct type.
Can't find a axel code.
And the differential is interesting, 3969278, F89 build, June 8 1969. Which is correct, my build date is 3rd week June 69. I have read that Canadian Cutlass's had Chevy rear ends.
Interestingly that diff is for 70-72 Chevelle's. Did find a site which had a 70 Chevelle that had that # with a build date in June 69, said it was built by McKinnon Industries of Canada.
They mentioned that several had no axel code or a code which could not be cross referenced.

Is the code ever found anywhere than the top of the PS axel? Any easy way to tell if its a LS?
Differential looks like it has never been opened.

oldcutlass

You can determine what fluid to use once you remove the cover. You can figure out the ratio by seeing how many turns of the tire vs turns of the driveshaft.

Yellowstatue

The axle code should be on the passenger side about six inches from the diff and upside down. Check both front and rear of tube.

Fun71

Well, if it leaves two black stripes behind the car on a launch, that's a very good clue that it's a limited slip.

old greybeard

will do, I had thought they were on top of the tube. Will clean the whole passenger side. 52 years of grime.

cjsdad

My 67 has a GM 12 Bolt and it looks factory, not sure. But the ID stampings are on the front of the passenger side tube.

monzaz

2.73 that is a Chevy 12 bolt rear.
Not even a POSI code....KDC is open 2.73 chevelle elcaminio - So I would say that is not going to do you anygood.
Open the rear and spin the ring around till you find some numbers on the outer diameter of the ring gear shoot a picture will decipher it

old greybeard

Found my axel code
Its the correct date and location for the build, Mckinnon June 17
Axel code is RA. Can't find a cross reference. Any ideas?

Fun71

I would expect the 2.78:1 ratio is actually a Type O and that listing is, well, a typo.

Yellowstatue

Per the chassis manual...Type "C" RA = 2.73 (41:15).

old greybeard

Thanks had found that site after I posted
It is a 69
2.73 or 2.78
Canadian car, Chevy rear end.

Fun71

Correct, there were 8.2" 10 bolt rears from Chevy, Pontiac, and Buick in those years. Different ring and pinion tooth counts gave similar, yet slightly different, ratios.

Yellowstatue

Cheese Norm, now I have to create a new folder for all these certificates I am being awarded with.

monzaz

2.78 will always be a B O P ratio (14 - 39 tooth count)
2.73 is normally chevy 10 or 12 bolt c-1lip rear (15 - 41 tooth count)
68-70 Buick did use the 2.73 also (8.25 odd rear large driver side carrier bearing 1.875 pinion shaft)
8.5 also used the 2.73 ratio and became a 3 series gear... lol.

Wacky stuff over the years.
then 7.5 10 bolt metric 2.73 became a 2 series gear ratio

Jim
JD Race