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65 had 2 different versions a Buick that had no casting ribs vs the Pontiac version that has a rib on the passenger side, in theory it gives more pinion support
65 Pontiac 1 rib:
Depending upon factory ratio 2.78 was a Buick casting 3.08 was both and 3.23 on up on used Pontiac versions
Why did GM use so many different but similar rear ends? While I can see maybe using different rearend design to fit different cars (leaf spring verses coil spring) it seems to me it would have been far cheaper to simply design one rearend for the stoutest engine/weight capacity, and use it across the production run. Think of the time and money saved only having to build and inventory one rearend?
If a rearend will survive behind a big block 4 speed, it would live just as easily with a 6 cylinder Powerglide. Just seems to me there were plenty of opportunities to streamline things back then. I can almost understand that way of manufacturing things today. With ever more stringent CAFE requirements, the added weight of overkill parts is more of a disadvantage.
Since I’m on this subject, why did GM use different transmission bolt patterns? BOP and Chevy, why?? In the later years with the 60* v6 engines, I assume they did it to help with clearance in the fwd cars. Once again, seems like missed opportunities to streamline production and inventory
Last edited by matt69olds; Apr 29, 2021 at 05:33 AM.
It was a Pontiac design based upon what I have read, back then each group of GM was treated as a separate entity hence 4 different 350 cubic inch engine engines. Wasn't until the mid-70's that they commonized engines and then got sued for putting a Chevy engines in Oldsmobile and what not.
I could understand the different length axle tubes. Seems to me if they had made ONE center section for leaf spring/coil spring cars, maybe one for trucks, and then pressed on the appropriate axle tubes could have cut way down on manufacturing costs.
Im sure there were and still are people who calculate the costs to the penny to justify the way things are done.
The late 50's early 60's full size Oldsmobile/Pontiac rears are different from the 8.2 version.
And Pontiac did use the same center casting on the Firebirds, my 67 had ears on it for control arm bushings, later on they cut and then cast that features off..
Also another dumb thing GM did, Chevy had it's own 8.2 which was weaker version.
It just took GM a long time to evolve from multiple companies merged into 1, Ford and Chrysler seemed to do that better,, although they had they're quirks as well
