i really want to find out what gears are in my diff but i have no idea how or what numbers to use, if someone could help me that would be great! thanks!

 

What year is your car? If you look on the passenger side axle tube, probably facing towards the rear (but also possibly facing forward), you might find a two-letter code or a letter-number code. That code will tell you the gear ratio in your differential (if someone hasn't changed it) as well as if it is a posi or open rear end. If you can find that code, post it along with the year and model of your Olds and someone here can tell you what that code means.

Randy C.

 

On my 74 the code faces toward the front of the car and is on the inboard side (close to diff) of the pass side axle tube. You may need to scrape around if it's greasy to find it.

Like Randy said, we'd be happy to decode it for you.

 

i got a few codes from the diff and the axle tube right where you said it would be. the numbers on the diff are 1234496, this was found on the oil cover. and 1235197 this was found on the passenger side of the diff on the side sort of of the pumpkin. the one on the axle tube was this SA 021 1, and it could have possibly been 0 SA 021 1 idk anything aobut these numbers or what they are supposed to look like but thats what was there. if you can get anything out of these that would be great. thanks alot its an open diff and i know that because i dont have a tag on my diff, but when i do burnouts only my right rear spins i need a posi haha

 

what you've got there is an open 2.78 rear end... i have the same one in my cutlass...

 

damn! thanks alot it seems kinda low, it has no problem smoking the tires... TIRE haha

 

You'd be surprised how it is easier to smoke the tires with a tiny ratio like that,compared to a steep ratio,like a 4:10.

 

The "SA" code tells me it is a 2.78 open differential from model years 1965 through 1971 ("O" type axle for '68 and '69) and a 2.73 open rear end for '72, all with drum brakes.

Randy C.

 

thanks alot guys! you really helped. so if i were to put a locker in my rear would my car still smoke 'em? and do you recommend a locker or tru trac by eaton?