I have a 1969 Cutlass and was wondering if there is a way to identify my diff with out taking the cover off and measuring the ring gear? I'm looking into buying a powertrax unit and need to know if its a 8.2 or 8.5 ring gear. The cover has 12 bolts which I know doesn't for sure mean its a 12 bolt rearend. Thanks

 

If it's a O-type (12-bolt cover/10-bolt ring gear) then it's a 8.5"
BUT that doesn't mean it can use the "corporate" Chevy 8.5" 10-bolt gear set. Olds rears use their own internal parts. If you're looking to install a Powertrax, I seem to recall Brian Trick saying the O-rear can use the 8.5 10-bolt kit. Check with Brian (507Olds) to be sure before you buy anything.

Here's a good identification resource: http://www.supercarsunlimited.com/in...id/diff_id.htm

 

Yes, it sounds like the factory Type O rear used from 1967-70. There should be a two letter code stamped in the passengerside tube. If it's not been messed with, this code will tell you the gear ratio and if it's a limited slip or not. John

 

12 bolt cover with bolt in axles is a Olds 'O' type with a 8.4 " ring gear really not a full 8.5 diameter Jegs and summit call it that ... ALL it does is confuse everyone in thinking it is like a corp 10 bolt 8.5 rear.

check out www.jdrace.com (ID DIFFERENTIAL ) 12 bolt 8.4 olds rear and see if the pictures match what you have.

Jim

 

Thanks Guys...This is some amazing usefull information. Thanks for all your help. The positrax I was looking to buy was an 8.2 which now I don't believe I have. Looks like I have the type O rear end with the 8.4

 

you need a 1920 10 bolt 8.2 unit

We have them instock all the time. Jim

 

The Type C 12 bolt cover has ribs between the bolts, and a big inverted V notch across it to channel oil out the axle tubes to the bearings. The Type O 12 bolt cover is smooth, with just a lip around the perimeter.

 

If you post a picture of the housing some of our cronies should be able to say for sure.

 

 

There it is.....What you think it is?

 

 

 

As you can tell , the pictures are not coming through , i am located in Hebron Illinois in northern illinois and have a selection of o-axle parts , if you want to look at them you will be able to figure out what you have . BOB