Hi there, Ive been doing work on my 442 and I wanted to figure out if it had a posi rear end. I cant just do a burnoit because the car isnt running currently. I jacked it up, put it in neutral and spun the tires. When I spin the passenger side the driver rotates in the opposite direction and when I spin the driver side the passenger doesnt spin at all. I think this means it doesnt have posi. Can someone confirm this? Also how hard would it be to put in posi? Thanks!

 

1) You are correct.
2) Check with @monzaz on this site. Parts for Type O rear ends are not easy to come by.

 

Verify the type of rear end under your 1968 442. If not changed by some previous owner, US built '68 442s came factory equipped with type "O" rear ends and Canadian built cars were equipped with the more common Chevrolet 12 bolt rear end.

 

How do I check?

 

If you jack up both sides of the rear, and put it in drive or in gear (be sure to chock the front tires), you can check some things. If you put a lug wrench on the passenger side lugs and try to tighten, one of two things will happen. If it very easily rotates the wheel forward, and the left wheel goes backward at the same rate, it is an open rear (or a failed limited slip). If you put torque on it and you can't move it until about 75 foot pounds, and then the wheel starts going forward with the other one going backward, and it continues to need that torque to do it, it is limited slip and you just tested the force setting.

If you put it in neutral and do this, it's a crap shoot on whether an open rear will spin the drive shaft, or spin the other wheel backwards, or some of both. In neutral, a limited slip wheel will rotate both wheels forward, and spin the shaft, as you are below the slip force.

 

I put it in first and was easily able to spin the passe ger side and the driver side spun in the opposite direction. If i underatand correctly this means its open dif. How hard would it be to swap out the dif for posi?

 

Depends on what rear it is. Once we have identified the rear, it would be within your capability to take the whole axle out of the car and take it to a rear end shop to be setup with the right parts. You'd need more tools and know-how to do it yourself.

 

I was able to convert my '69 4-4-2 with an open O-type 3.23:1 differential to an anti-spin 3.23:1 differential with a carrier kit that was offered by Supercars Unlimited (no longer in business). I don't know if other vendors or people on this site offer the same thing but my guess is that someone still does. What I got was a complete new original style carrier assembly in the original style, ready for installation, with a case shim assortment, carrier bearings/race and ring gear bolts. I'm not a mechanic; I had it installed and it is now nice to have, although in nearly every circumstance I've been in with that car I've never needed it!

Randy C.
'68 4-4-2 convertible (that originally came with anti-spin)
'69 4-4-2 convertible (that now has anti-spin)

 

We have the Posi units as per the FOR SALE platform on this site.
I have rebuild kits and Aftermarket 3.42 and 3.90 gears
I have Axle shafts
and Axle shaft bearing kits...
We have just about everything...BUT the only thing with the 12 O it is a bit more expensive than other rears.

 

Gear ratio will be stamped into the outer edge of the ring gear (it will have the tooth count of the ring and the pinion ) Example 13 40 (means 3.08) along with the date and month and gm part number for the ring gear.
Jim
JD Race

 

Look at the rear axle cover - see photo.
Also - the type O vent will be on the axle tube, the type C vent will be on the center casting.

 

Its a type O according to the diagram

 

I think I am going to hold off on the posi until I go to swap the current Js for the correct C heads.

 

Well, if you don't get rid of those J's, chances are you won't need a posi anyway.

 

Actually, you just gave me a piece to a puzzle unexpectedly. My 68 is a restomod with Yukon a 3.73 gear set and axles and it needed a pinion seal. I was wondering about where the actual axle housing came from as it's obviously not aftermarket but I can't find any identification on it at all. It's a bit pitted and has been painted.so whatever markings it had are not visible.

The car was made in Canada, maybe that explains the standard Chevy 12 bolt rear end.

I know there are a couple of guys who decode Canadian VINs and just haven't got around to that yet. the car's not particularly original so I wasn't sure if I wanted to bother. Do you know if that would include info regarding it's original drivetrain ?

 

If your GM car was built or sold in Canada, you can get it fully decoded here:

https://www.vintagevehicleservices.com

Definitely includes all pertinent info relating to drivetrain along with whatever other options the car was ordered with.

 

The GM of Canada info will have the original gear ratio

The Oshawa cowl tags have more option info than a BOP or Lansing tag but I don't think they have the gear ratio