Im looking to upgrade gears in my diff as well as get a posi carrier for it. The car is a 69 cutlass and im pretty sure its still got the original diff, but I dont know for sure. I need to know if its a type "O" diff or not before I start looking for parts. The casting number on the housing is 402227. Any help decoding that would be appreciated.

 

What is the letter code stamped in the right axle tube? Is it a 10 or 12 bolt cover?

Most 69's had a O type 12 bolt cover rearend.

Greg Rollin at Supercarsunlimited.com is a great source for this info and parts.

 

Its a 12 bolt cover. I cant find any numbers stamped on the axle tubes (i used a wire brush to clean all the crap off but i still cant find any numbers).

 

It will be two letters stamped on the right axle tube between the center section and the right shock mount. It can be on the front or on the rear of the tube and is often upside down. Usually about mid tube and most I have found are on the back side.

 

I spent almost an hour cleaning all sides of the axle tubes with a wire brush and they are now totally clean but i cant find any letters. How big are the letters that im looking for? Btw, i did some research on the differential housing number and it said that the number 402227 was from 70 which would make it the type "o" rear end. Im not sure how reliable that website was though.

 

BAck side passenger tube faces the back of the car. will mostly be upside down ??? why I do not know.

letter size ( T Y ) THIS IS THE ACTUAL SIZE!