Is it possible to make a 1967 A body posi fit under my 72 Cutlass. I hear that it is narrower than mine, hence possible tire to frame clearance issues. What about driveability? Will a narrower rear give me other issues? Can I use wheel spacers?

Thoughts please,,,

John

 

Its a direct swap.

 

Two things to watch out for. First is the obvious narrower track. Many people use this to their advantage so they can run "deep dish" wheels on the back. Personally I like the look of a lot of offset on a rim, but you can make the tires fit with the correct offset and the original axle. The second thing is the pinion flange to axle centerline dimension. The various GM axles have different dimensions here that can require differences in driveshaft length. If the driveshaft is too short it can fall out of the trans output shaft (or at least leak trans fluid) and if it's too long you'll damage the pinion bearings.

Don't ask me how I know this...

 

What about taking the posi unit out of the one rear and placing it in the other????

John

 

Documentation please???

John

 

the 67 is a 1/4 inch shorter than the 72, which makes it a 1/8th inch shorter on both sides, i swaped on into a 68 and love it.

 

I heard it was 1" total or 1/2" on each side.

Still not clear...

John

 

John, I wish you wern't on the other side of the country, I'd swap you a newer posi for your 1967 and find something to trade for the 4 speed you'd mentioned in a different post! I believe that rear end would fit fine and unless you wanted to put some large tires underneath I don't think the offset would be a problem. The wheelwell on my 1971 Cutlass Supreme is about 14 inches wide! I've tucked 295's in there but when the body rolled the inside of the tires rubbed. That's about a 12" footprint, so if you were to use something more like a 245 I think you'd have room to spare with the narrower rear end. John

 

I really apprectiate that. I wish that were the case as well. What do the transmissions weigh out at? I have lifted a 3 speed and it does not seem to weight any more than a head. I know 4 speeds have more parts (obviously) but how much more heavier are they.

I use Fed Ex to do all my "heavy lifting" under 70 lbs. They take heads and cranks all day long. In fact it is only about $40 to ship a head coast to coast via fed ex. I've done my homework in this department.

ANYWAY I digress from the topic at hand. I guess If I WERE to fit it under there I would have to measure the "pinion flange to axle centerline dimension" Joe mentioned.... I know getting a custom fitting driveshaft is a matter of FINDING the place to get it done.

I have a lead on a guy who might swap me one for one for the correct unit, but who knows how that will pan out!

John

 

The width of the early vs. late axles has always been a little uncertain to me. I too have heard the 1 1/4" difference, and I know the frames of the 64-67 cars were slightly narrower, but I also know that the Type O axle was used starting in mid 1967. I have a 67 Type O housing that I personally removed from a 67 convertible parts car and I know it was the original axle in that car. It is the same width flange-to-flange as the 68-70 Type O axles. I also know that the factory parts book lists the same part number for the 67 and 68 Type O housings.

 

Another thought to consider John, you should have the corporate 8.5 10 bolt under your 1972 Cutlass. I read somewhere that GM used that rear end under lots of models including the 1/2 ton pickup and vans up to about 1989. That, supposedly you could pull the posi unit out of a van and have it installed in your Cutlass rear end. A little more work to do, but it may be easier to find that posi unit and have it shipped than the whole rear end. Joe, do you know if that's right?

 

Your talking about the internals correct?

I'm going back out there and measure EVERY possible dimention of this bad boy some time this week. If I fall somewhere within say 1/2" and the snout has the same centerline dimension than I am probably going to bolt it in.

Did I mention anywhere that I scored this rear end for a mere $50?

John

 

That's correct. The 71-up axles are "corporate 10-bolt" carriers. Internal parts (posi carriers, gear sets, bearings) are readily available.

 

my car is a 68 olds cutlass s canadian build car with a factory chevy 12 bolt rear end i measured and swaped out the rear end foe a 67 chevy posi 12 bolt rear end out of a factory 67 442 canadian car. the naxle housings are a 1/8th of an inch shorter on both sides, materafact when i put the rear sway bar in the car it was a snug fit. i didn't need to put those nasty shims in that rust out the control arms. and sa for referance i abtained my ase certification in searing and syspension in 99. i also added polyurithane bushings front and rear new springs and shocks added disc brakes in front had the frame off the car sand blasted and primed painted and rubber caoted, its going to be a driver. with 215 70 14 firestone tires on factory 70 super stock 2 rims i have 2 1/8th inches to the inner side wall of the tire.