71 & 72 LeMans - 350 Chev vs 350 Pontiac

seventy2plus2 · Canadian Poncho Superstar!

71 & 72 LeMans - 350 Chev vs 350 Pontiac

4SPEED427 · A Poncho Legend!

I'm not sure how much help this is, but 25 years ago my boss had an all original 72 GTO 455 Canadian car and it had the common 12 bolt in it, the same as a Chevelle.

73SC · A Poncho Legend!

1970's from Oshawa had the Pontiac engine, In 71 and 72 the sbc was used. The frames for the entire A body line are the same. There are plenty of reports of even Oldsmobile Cutlass cars out of Oshawa with Chevy diffs. I think typically yes the BOP was brand specific and power train specific but as we all know all bets are off on an Oshawa production car.

While I have a Chevy powertarin in my LeMans I know the differentials from the Cutlass, US LeMans and Regal/Century interchange.

73SC · A Poncho Legend!

Carl Stevenson wrote:

I'm not sure how much help this is, but 25 years ago my boss had an all original 72 GTO 455 Canadian car and it had the common 12 bolt in it, the same as a Chevelle.

Carl, I believe GTO's were only made in Oshawa in 1970 and 1973 so your Boss's car was a US made car, that being the case your observation of the Chevy diff is even more intersting.

4SPEED427 · A Poncho Legend!

Sorry, I should have been clearer. This was a GTO sold new in Canada. I have no idea where it was built, but it was a Canadian specification GTO. It would have option code Z49 on it I think as do all the Canadian cars of that era.

No question about the part of the 12 bolt being original.

I once read that the 72 455 Goats all had 12 bolts.

4SPEED427 · A Poncho Legend!

73SC wrote:

1970's from Oshawa had the Pontiac engine, In 71 and 72 the sbc was used. The frames for the entire A body line are the same. There are plenty of reports of even Oldsmobile Cutlass cars out of Oshawa with Chevy diffs. I think typically yes the BOP was brand specific and power train specific but as we all know all bets are off on an Oshawa production car.

While I have a Chevy powertarin in my LeMans I know the differentials from the Cutlass, US LeMans and Regal/Century interchange.

I'm not sure on the 70 and up Canadian Cutlass but there is no doubt about the 68 and 69 cars having 12 bolts in many instances. My brother ended up with one in his wrecking yard. It was a 6 cyl 2 door hardtop with power windows and a 12 bolt!

73SC · A Poncho Legend!

Carl Stevenson wrote:
I'm not sure on the 70 and up Canadian Cutlass but there is no doubt about the 68 and 69 cars having 12 bolts in many instances. My brother ended up with one in his wrecking yard. It was a 6 cyl 2 door hardtop with power windows and a 12 bolt!

I agree, reports I have read are on 68 and 69 cars.

Ghost Post · Poncho Master!

Although stout units on their own, always be clear the Type Olds 12-Bolts actually have a 10 Bolt ring gear when you open them up..

Canadian Poncho · A Poncho Legend!

I understand Canadian built Buick GS' also had 12 bolt diff's as well wheras all the U.S Gran Sports did not.

Astro Jet · Poncho Master!

A body chassis (Chevelle, Lemans, Skylark, Cutlass) are the same and interchangeable for 64-72. One of the most brilliant engineering moves GM ever made and one of the reasons they were king of the world at that time.

The only difference between a Chevy powered or a Pontiac powered Lemans chassis were the engine mounts. As for rear ends, generally Pontiac powered cars would have received the Pontiac 10 bolt and Chevy powered cars the Chevy 10 bolt. The rear suspension mounting systems were the same so you could easily swap between different rear ends. All Lemans' which came with any variant of the 455 came with the "corporate" (Chevy) 12 bolt as standard equipment. (Pontiac did not make their own 12 bolt as Oldsmobile did).

455gto · Poncho Master!

Astro Jet wrote:

A body chassis (Chevelle, Lemans, Skylark, Cutlass) are the same and interchangeable for 64-72. One of the most brilliant engineering moves GM ever made and one of the reasons they were king of the world at that time.

The only difference between a Chevy powered or a Pontiac powered Lemans chassis were the engine mounts. As for rear ends, generally Pontiac powered cars would have received the Pontiac 10 bolt and Chevy powered cars the Chevy 10 bolt. The rear suspension mounting systems were the same so you could easily swap between different rear ends. All Lemans' which came with any variant of the 455 came with the "corporate" (Chevy) 12 bolt as standard equipment. (Pontiac did not make their own 12 bolt as Oldsmobile did).

So on any 12 bolt Pontiac........It's a Chevy? Were the trannys any different (350's)

pontorquer · Poncho Master!

My 1972 Luxury Lemans 400 sport coupe was built in Oshawa and came with the 12 bolt chevy rear-end, I have seen 2 more of these Oshawa built Luxury Lemans 400 YS/7K3 heads 4 barrel Qjet, over the years and they also had 12 bolts. We were fortunate here in Canada to get these beefy rearends in all kinds of Oshawa built GM products between 1968-72, I have even seen 68 Beaumont 307 with 12 Bolt and 68 Olds Cutlass S as well. In the states, The 70-72 GTO's- Lemans had Chevy corporate 12 bolt only in 455 equiped cars.