I have a 71 cutlass s, 350, auto, non-posi 2.56 gears.I want to put a diff from a 70 chevelle. This is a posi with 3.08 gears. what kind of trouble will I have when I try to put it in.

 

If it's the entire axle it should be a direct swap. Are they both 10 bolts?

 

Yeah they are both 10 bolts.I had to make new spring seats and weld them on because on the cutlass they sit farther ahead than on the chev.the lower control arm hangers look like they are farther apart on the chev I think I should move them closer before I try to install so the control arms will fit without a problem.

 

The rear suspension, control arms, and spring seats are IDENTICAL on all 68-72 A-body cars. If you had to move the spring seats, one of the two axles is not from an A-body.

 

I'm pretty sure that the rear end in the car is original.The one that I want to put in, I got from under a circle track car.I was told it was out of a chevelle.I'm having a hard time reading the ID numbers on the axle housing.The rear end looks the same other than some slight differences in measurements

 

The measurements should be the same between the two axles period.

 

Do not be surprised if you need a crossover u-joint.