G body vs A Body Rearends

August 6th, 2004, 01:57 PM

Would an 8.5 10 Bolt from a G-Body (1984) work in a 1972 Cutlass A-Body? I understand that the '72 has a 10 Bolt (8.5?), but it's a 3:08 open diff. The 8.5 is a 3.73 Posi. Could I swap the G-body rear into the A-body?

GoldOlds · May 21st, 2007, 09:28 PM

I could be wrong here, but I think most G-body ('78 to '88 Cutlass, Monte, Grand Prix, Regal, Malibu, etc.) rears have 7.5" rear ends, not 8.5". The 7.5" is the weakest rear end GM ever made. The only G bodies that had the 8.5" rear were the 442s and Grand Nationals/Turbo Regals.

joe_padavano · May 22nd, 2007, 10:45 AM

While there are a few 8.5 inch axles under G-body 442s and Turbo Buicks, almost all came with the 7.5 inch axle that was originally born under the Vega. More importantly, the G-body axle is about 3 inches narrower than an A-body axle AND the control arms are at a different angle. You can physically force them into place but the suspension will bind up if you try to drive it.

GoldOlds · May 22nd, 2007, 12:16 PM

Quote:

Originally Posted by joe_padavano

the 7.5 inch axle that was originally born under the Vega.

That's exactly where those P.O.S. rears belong! Too bad the G-bodies didn't ALL come with the 8.5" rear - otherwise, they're great cars.

- GoldOlds

monzaz · September 13th, 2007, 10:06 PM

What I could never figure is how camaro and trans ams got totally left out of the 8.5 loop??? That was weird. JUST a thought. Jim

May 22nd, 2007, 10:45 AM	#3 (permalink)
joe_padavano Super Moderator Join Date: Mar 2007 Location: Northern VA Posts: 4,331	While there are a few 8.5 inch axles under G-body 442s and Turbo Buicks, almost all came with the 7.5 inch axle that was originally born under the Vega. More importantly, the G-body axle is about 3 inches narrower than an A-body axle AND the control arms are at a different angle. You can physically force them into place but the suspension will bind up if you try to drive it. __________________ Joe Padavano 64 Jetstar 88 Conv 66 442 L-69 Conv 68 W-30 69 H/O 69 442 70 W-30 72 442 84 Custom Cruiser 86 Caprice wagon (w/307 Olds)

September 13th, 2007, 10:06 PM	#5 (permalink)
monzaz Registered User Join Date: Jul 2006 Location: Richfield, Oh Posts: 204	8.5 rear What I could never figure is how camaro and trans ams got totally left out of the 8.5 loop??? That was weird. JUST a thought. Jim

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August 6th, 2004, 01:57 PM	#1 (permalink)
<72S> Guest Posts: n/a	Would an 8.5 10 Bolt from a G-Body (1984) work in a 1972 Cutlass A-Body? I understand that the '72 has a 10 Bolt (8.5?), but it's a 3:08 open diff. The 8.5 is a 3.73 Posi. Could I swap the G-body rear into the A-body?

May 21st, 2007, 09:28 PM	#2 (permalink)
GoldOlds Senior Member Join Date: May 2007 Location: Chatham-Kent, Ontario Posts: 117	I could be wrong here, but I think most G-body ('78 to '88 Cutlass, Monte, Grand Prix, Regal, Malibu, etc.) rears have 7.5" rear ends, not 8.5". The 7.5" is the weakest rear end GM ever made. The only G bodies that had the 8.5" rear were the 442s and Grand Nationals/Turbo Regals.