VI Cutty

Going to check out what is supposed to be a 70-72 vintage 10 bolt posi from a Skylark (don't know what the axle code is on it yet) for use in my '71 Cutlass S with an eventual upgrade to a 455.

Seems to be a straight bolt in, but would the driveshaft length need to be modified?

Would this be worthwhile pursuing or would I be better off upgrading the original rear end that's in the car now to a posi?

70cutty

I would just upgrade the existing one. You don't know what kind of condition that posi is, also it might ne a 8.2 rear.
You might end up on square one with a rear end that needs to be rebuilt or a weaker one.
I bought a rear out of 71 cutlass to replace my 70 O-type, bought parts from monzaz - Jim and had it installed locally. Everything was around $850 installed.

Fun71

I'd at least take a look at the Skylark rear. If the price is right, I would buy it even if I didn't need it (I have 3 sitting behind the garage now).

VI Cutty

Took a chance and bought it, figured the price was right. Now I just need to get hit home and figure out what I've got!

If nothing else, I now have an aluminum tag that reads "Use Limited Slip Diff Lube Only" :-D

The casting number is 1243774, and the only stamp obvious on the axle housing (passenger side, front, center line) is "CE". Anybody able to help narrow this down?

oldsmobiledave

Every 1971-72 Buick 10 bolt 8.5" diff that I have ever seen has a 3 letter code not a 2 letter code. They all start with L and end with B. I suspect that diff is not original to the car you pulled it from.

1969w3155

Doesn't appear to be a Buick rear: http://www.buickperformanceclub.com/axles.htm

1969w3155

There appear to be other letters/numbers to the right of the "CE" stamp, do you know what they are?

VI Cutty

The spring location and a couple other things don't seem to match up. I'm leaning towards it being a '74 rear end, possibly Buick.

1974 A&G Body rear end codes: http://www.pontiacpower.org/74axle.htm

This page lists a CE code for a "Perf. Ltd. Slip" differentiated from a "Standard Ltd Slip" on the '74 models. I'm assuming Perf = performance: http://www.buickgod.com/article/3523.html

Based on what I'm seeing and assuming it is a '74 rear end am I correct in believing it won't work in my '71? Can the gears be swapped?

VI Cutty

It's hard to say if there are or not. If there are, they're not as well defined as the CE. I'll give it a better cleaning and look when I go to pick it up.

1969w3155

Chevy used a CE code for a couple of years (3.08's) but the casting numbers are different. www.chevellestuff.net

oldsmobiledave

swap the carrier & gears into your housing, if they are both 8.5"

VI Cutty

Looks like it was used on mid '60s Chevelle rear ends. I'm trying to find comparable axle setups (shock/trailing arm mount, spring location, etc) to narrow down the application.

That will be plan B once I check out the specs on this rear end and what's in the car now. Plan C will be to sell the posi and recoup my cash which shouldn't be hard to do.

VI Cutty

Looking at my photos last night, there's a K (GM Canada) pretty clear to the right of the CE. In addition to the '74 Buick use of the CE code I found a Pontiac reference to the same code as posi in '73/'74 A and G bodies, with 3.23 gearing.

I need to get under my car tonight and determine what rear end is in there now; from the information I've seen I expect to find a corporate 8.5" ten bolt non-posi. Photos of diff covers posted elsewhere here seem to match the one on mine. (https://classicoldsmobile.com/forums...tml#post804269).

I don't expect the new rear end to work in my car, but now have my fingers crossed that both are 8.5" so I can just swap the guts as suggested.

VI Cutty

Here's what's in my Cutlass now, can't quite get at the axle housing to get the id stamping. Have to turn the car around tomorrow to make more room. Does this look consistent with the 8.5" 10 bolt? I keep finding conflicting information out there.

monzaz

This rear is a 1973-1977 era A-body gm 10 bolt 8.5 rear.

It will not bolt into a 1964-1972 era A-Body chassis.
Shock mounts are in the front, spring perches are over the center of the tube not off the front as a 64-72 gen should... upper control arm mount bosses are wrong cast position too wide and too low on the center casting...Not going to fit a 64-72 era a-body car.

VI Cutty

Yeah, I noticed all those differences once I got it home and started comparing it to what was in the car. No problem, sold it and made a couple bucks. :-)