I have come across a 8.5 posi rearend out of a Grand National. The only problem is that it needs axles and backing plates. Does anyone know if I can swap the axles and backing plates out of my 78 Monte, or do I have to go with actual Grand National axles? Are they bigger or do they have more splines?

 

well if i remeber right the 7.5 10 bolt rear end has like 27 splines and the 8.5 10 bolt has i wanna say 32 but that doesnt sound right i know they are different

 

what i did to find out is go to summit put in each car and look at the rearend stuff

 

Know the backing plates are the same, axles should be . Think they are both 28 spline, some of the early 7.5 ones may be 26 ,but cant remember for sure.

 

I think I figured it out. The Grand Nationals came with a 8.5 that had 28 spline axles. The 78 Montes came with a 7.5 but the axles were only 26 splines, so I will have to buy new axles. I wish iwould have kept my other rearend, I could have used the backing plates off that one, instead of my original rearend. Thanks for all the help.

 

I just spoke to the guy that has the rearend. It has 3.42 gears and is a posi, and he wants $400 for it, but it doesn't have axles or backing plates. Does that sound good or what?

 

400 for a housing and a diff... doesn't sound too bad but you'll have to spend some more $ to get it going

 

Ya, I would snag it up in a heartbeat. still have less then 600.00 in a 8.5! good deal.

 

its a good deal but you could pick up a 28 spline carrier and axles for your current rear. the down fall would be that it still only has a 7.5 ring gear and there really isnt a point to throw money into it.

 

Yea, what he said....
Then you wont have to remove the axle from the car and no brake plate transplants.
It depends on what your using it for.... A street car? Are slicks ever gonna be used? Small or big block & power/ torque rating.