Hello All,
I recently picked up a nice Olds 31 spline posi unit carrier w 3:91 gears from a buddy c/w the 31 spline axles. My question is....can I use these pieces in any 1968 Olds Cutlass type O rear end or do I need to find a specific rear end assembly that will accommodate this carrier? Any assistance is much appreciated- thanks!
Brad

 

You can install that carrier in a 28-spline housing. You will need carrier bearings #LM102949,and bearing races #LM102911. Then you will need 31-spline axles,which can be made by Moser or other companies.

 

I think he said he has the axles WHICH he can use also in the 28 spline housing. So your answer is yes on every thing.

The normal bearings used on the 672 case are A36 set which is the same as 12 bolt chevy...Brian is using the spool bearings for the 8.5 and or eaton bearing set-up which has the larger inner diameter hub and still keeps the outer diameter diameter to fit into the carrier saddle of most ten bolt GM rears. These bearing change the pitch fo the bearing slightly and are more smaller diameter barrel bearings - that is how they can do it.

remember to get that pattern right take your time and shim it correctly do not waste the gears as they are getting hard to find these days.

Jim
JD

 

Awesome- that was the answer that I was hoping to receive!!
Great info guys! Now where can I buy these bearings?
Brad

 

Any local auto parts store should be able to get them. Just give them the numbers Brian provided.

 

Understood- thanks! I will try going to the Napa store not far from me later in the week.
Thanks again.
Brad

 

The bearings are usually on the shelf,but the races might need to be ordered. The races you need are LM102911. Do NOT confuse this with the LM102910,which is usually in the shelf,but narrower,and will not work.
If you have the original 31-spline axles,then you will need to use a 67-69 housing,that uses the same RW507CR axle bearing.It sounds like you are using another 68 housing,so you're good there.

 

Thanks Brian. Yes the axles given to me are the GM 31 spline taken from a 68' parts car many yrs ago. I believe the rear end housing that I have is a 28 spline unit taken from a 68' Cutlass S. Are there any serial numbers or markings that I should look for on the outside of the rear end housing that will confirm it is a 68' or 69' rear end?
Brad

 

Easiest thing to do is pull an axle shaft to see if it has the same bearing as the 31-spline axle.