what 8.5" WILL fit?

[grand86prix_05]

Yeah I'm thinking I would probably still grab it, if anything I can easily get my money back even if its an 8.2. He said he just wants it out of the way.

Do the 8.2s need a shorter drive shaft? Just in case that's what it is.

 

[pontiacgp]

Crap...I don't want to have to shorten my drive shaft. Well I assumed it to be an 8.5 anyway, he said 10 bolt out of a 72 chevelle. Sounds like I may have to back out of the deal, sucks though because he only wants 100 out of it. Then again I could probably sell it for a good chunk more

You won't have to shorten your driveshaft. I switched out the 7.5 for a 10 bolt chevelle rear end and I used the same driveshaft. You will probably need a conversion u-joint.

 

[grand86prix_05]

Alright I located a 12 bolt out of a 72 monte carlo, anyone know the ratio or width? Better yet anyone have a list of 12 bolt specs where I can compare lengths and all that? Guy is only wanting 250 but I would like to know a little more about it

 

[JBreu]

78-88 Gbody 10bolt ---> 58 inch wide
64-67 Abody 12bolt ---> 60.5 inch wide
68-72 Abody 12bolt ---> 62.5 inch wide

with 8.5 10bolt, you need to shorten driveshaft 1 inch over what you had with 7.5 10bolt
... I don't know what it is for a 12bolt

Khan posted the different width's here...As far as the gears gop, that depends on the motor/transmission in the MOnte..Best way is to pull the cover and count the teeth on the ring/pinion gears......for $250.00 that's a steal, even if it's an open differential. I have a 12 bolt in my car from a '69 Chevelle, the same as the rear you found and it fits great.... 8)

 

[grand86prix_05]

Right I'm not trying to sound like a broken record, but I am finding so much mixed up info on these stupid things. I was told montes might be a different width so wanted to check, but I think I pretty well have it cleared up. And not to question anyones input, but I found somewhere that said the 72 12 bolts were 61" rather than 62.5". Checked a jegs book which said the axle shafts are right around 30 inches a piece plus give an inch for the center rod in the carrier and get about 61 inches. So essentially would be adding an inch and a half per side. That would probably be perfect for me so I am hoping that's right but I would just really like to find a direct list of info on these things

 

[khan0165]

you bring up a good point... the 70-72 Monte Carlo was marked as an A-body platform, sharing it's chassis and wheel base from the equivalent Chevelle/Skylarks/Cutlass/etc...
however, the Pontiac Grand Prix of the same era, was then named a "G-body" (but not to be conpared with our G's, this platform was very different). The chassis began as the A's of the Monte/Chevelle/Skylark/Cutlass, but Pontiac extended the rails, changed the wheel base, and made some other mods... thus not to be considered an Abody.

... so I wonder if the differential lengths were also changed?

 

[grand86prix_05]

Interesting, if you ask me gm made too many different yet similar platforms lol well I offered the guy 200, he said he'd take 225 and would hold it til Saturday so either way its what I'm going with. Can't wait to get it homeless and get it set up for my car

 

[khan0165]

yeah, the Abody platform started in '64 to '67 with the Malibu (Chevelle), Skylark (GS), and Cutlasses. In '68, they changed the wheelbase and another few dimensions to accommodation the new body style.

in '70 they introduced the Monte Carlo and simply borrowed that '70 A-body platform to mount the Monte's body. But Pontiac took a different route with the Grand Prix. They wanted a longer front end, so they modified the rail lengths, changed the wheels base, and I guess a few other changes were made. So '70 to '72 Grand Prix was named a "G-Body" platform, even though it was just a mod'ed A-body.

I believe Mopar did the same thing between the Dodge Challenger and Plymouth Cuda at the time. The Cuda used the Challenger's chassis, but with shorter wheel base and different rearend location.

 

[pontiacgp]

😳

 

[robhowardiii]

The u joint I needed for an 8.2 out of a 68 chevelle was 3-3130 from autozone