REAR AXLE INTERCHANGE

HI, NEW TO THIS FORUM AND TO B BODIES, MY QUESTION IS WILL A 1973-1977 GM A BODY 8.5 REAR END BOLT INTO MY NEWLY AQUIRED 1985 LeSABRE COUPE? I WANT TO TURN UP THE WICK UNDERHOOD AND THE 7.5 CURRENTLY UNDERCAR WONT LAST LONG.. BEEN DOWN THIS ROAD BEFORE WITH MY G BODIES. I KNOW IF I SWITCH TO THE 8.5 I WILL NEED THE DONOR CARS DRIVESHAFT.

THANKS FOR YOUR HELP

Welcome to the Forum!

If you want a direct bolt-in, no, it won't work.  You'll need one from a 77-96 B-body.

Here's what to look for:

Axle Ratio RPO Code Ring/Pinion Teeth Application
2.56 GM8 41/16 Std. Roadmaster LT1
2.73 GU2 41/15 Std. Caprice L99 (exc. 9C1)
2.93 GW9/GU3 41/14 Std. Caprice LT1 (exc. 9C1), Opt. Roadmaster LT1
3.08 GU4 40/13 Std. Caprice 9C1/LT1 (Police), Std. Impala SS
3.23 GU5 42/13 Opt. Caprice L99, Std. Caprice 9C1/L99 (Police)
3.42 GU6 41/12 Std. 91-93 Caprice 9C1/L05, Std. 94+ Fleetwood w/V4P
3.73 GT4 41/11 Std. 91-92 Fleetwood Brougham w/V4P

*V4P = 7,000 lb. trailer towing package... look for a hitch.



I think your Caps Lock button is stuck......

Hes just mad at us already lol just kidding, anyway welcome aboard, glad you found us!
And if your out searching for a rear end in a junk yard, those RPO codes Sweet posted are located on the trunk lid

Thanks for the warm welcome and sorry for all the caps....
I remember reading in a magazine some time ago that the 1973 to 1977 GM A Body rear was a bolt in deal, do you know what obstacles I may encounter going this route? Now again I'm not at all that familiar with the B Body, but is one of the issues the wheel bolt pattern? If I remember the A body coupe and sedan used the 5x4.75 bolt circle whereas the A Body wagons and B Body used the 5x5, when they switched to the 7.5 rear I think the B Body went to the 5x4.75 pattern.
I can get a very rough but complete 94 9C1 for cheap that would probably be the way to go
Thanks

Nope they are not a bolt in, the mounts for the shocks and springs have to be relocated which means cutting and welding.
As far as the bolt pattern goes, to my knowledge only wagons, 9c1's, and the impala ss's only got the 5x5 bolt pattern, all the rest had 5x4.75. But i also heard or read somewhere that the models that had the HD 11'' drums also had the 5x5 pattern.

I just swapped in a rear end from a 96 ss in my 79, check it out if you havent yet
https://www.gmbbodyforum.com/t153-gm-85-10-bolt-swap-from-a-96-impala-ss

Thanks for your help, I almost purchased a rear out of a 1976 Cutlass thinking it would fit.. That would have been a real bummer when I tried to install it in the 85 LeSabre...
I bought that 94 9C1 Caprice for real cheap, its complete!
Again thank you for your knowledge and I just might pick your expertise one or twice again..

I'm glad we were able to help.

Let's see some pics of a posi burn-out!!  LOL!!