Oldsguy1978

I have a 1982 olds cutlass supreme with the factory one wheel wonder. I'm tired of spinning. I found a 1984 Monte Carlo SS that's being parted out.

My questions are: this SS "should" have a posi rearend. How can I tell for sure? Also, will the whole rearend be able to bolt right to my cutlass?
​​​​​​I have a th350 and want to still drive it on the highway.

Thanks for all of you input!

joe_padavano

With both wheels off the ground and the trans in PARK, try to spin one wheel. If the other turns in the opposite direction, it's not posi. If you can't spin it, it IS posi. Now put the trans in NEUTRAL. If the opposite wheel turns in the same direction, it IS posi. Yes, the Monte axle bolts in.

brownbomber77

Instead of using another weak 7.5 with I think the cone posi, try using a Mustang 8.8 rear axle, something with 5 lugs ('94-'04). They bolt right in with little modification.


Redrill axles $115 http://www.rottenleonard.com/Drill-guide-price.html


Weld on spring perches (17 3/8 from center diff bolt to center of spring mount) $30
https://www.speedwaymotors.com/Speed...Tube,3527.html


Use spherical bearings for the upper control arm bushings on the housing $81
http://www.ebay.com/itm/8-8-Axle-Sph...ZXDMyK&vxp=mtr


Otherwise the brake line event bolts right into the factory center line.


$225 plus the cost of a stronger disc brake posi rear which is about $300 for a good gear depending on where you're located.

oldsmobiledave

Just buy a G body 8.5" posi from an 84 HO or 85-87 442 or an 84-87 Buick GN or Turbo T. You will need driveshaft mods too.

joe_padavano

Have you priced those lately? When they (rarely) come up for sale, the seller is always asking stupid money. $1200 for an 8.5" axle???

olds 307 and 403

That is a direct swap. It should have 3.42 gears but may be open but will have the bigger 7.625" spider gears and is stronger for that reason. How tall are your rear tires?

oldsmobiledave

The 8.5" factory G body diff is expensive because it is a bolt in that will be safe down into the 11s. It is simple supply & demand economics.


Have you priced an aftermarket replacement lately? The G body 8.5" is a bargain at $1200.

joe_padavano

The OP was asking if a Monte SS rear will fit. We have no idea if he wants or needs a $1200 axle.

monzaz

I usually just install a posi and gears and be done if all you want to do is spin the tires. IF you are DRAG racing at a track every weekend then you had better up grade to a better (NEWER REBUILT) larger rear end.
Guys please stop installing these USED rears that are 20 years old and out of junk yards your just asking for MORE headaches. Please rebuild them first...
Just because something is bigger does not mean it will hold up better when it is 20 years PLUS in age or higher / unknown mileage.

Good luck on the choice.

I have deals on 7.5 posi and gears hear for that Cutlass rear if you want to try that route...
PS Just because a car is a SS model etc. does not mean it has posi... you would think that but most of the 8.5 cutlass rears 84 -87era were open NON posi...

Jim Mitschke
J D

oldsmobiledave

In my opinion the 7.5" differential is a waste of time & money. Upgrading to an 8.5" diff is money well spent. I've never been disappointed with my choice to over build a driveline part.


You seem so hung up on the price of a G body 8.5" diff it's obviously a pet peeve of yours'. You are keeping the "Oldsmobile guys are cheapskates" label alive & well Joe.

brownbomber77

Forgot about this. Well, I paid $20 for the driveshaft flange and $7 for the conversion U-joint. Otherwise the driveshaft is the same length. You're still under $700 plus some time for a significantly stronger rear end AND disc brakes.

brownbomber77

https://gbodyforum.com/threads/8-8-i...p-enjoy.17317/