Looking in the parts book, for 1969-70 the available ratios were:
2.29, 2.56, 2.73, 3.07, 3.31, 3.55
Most Turbohydramatic cars were 2.73 and Powerglide cars were 3.07. M20 cars were 3.31.
But that leaves 2.29, 2.56, and 3.55. Does anyone know how one would have obtained those ratios? The "Accessorizer" that North posted doesn't show any optional ratios available for order, either. I'm just looking at 12-bolt.
-- Edited by davepl on Wednesday 14th of March 2018 01:29:20 PM
We were not always known for offering as many options in the U.S. Sometimes though we did get the same drivetrain choices as in the U.S. and I believe that in the case of 1969 full-size models we can go by the list shown below (source: GM Heritage Center)
Of course the 327 & the LM1 350 weren't used on the 1969 Canadian Pontiacs, the base V8 that year was the L65 350 2-barrel. Simply treat the L65 on the chart as the 327 section with it's lighter duty driveline components & eliminate the LM1.
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It is also worth mentioning that the 2.29:1 axle ratio was only offered on big blocks with Turbohydramatics. It was actually a 12-bolt with a smaller ring gear in order to achieve the tall ratio.
Bear in mind that I am using Chevrolet's U.S. drivetrain chart, not an official GM Canada chart. It is worth mentioning that by 1969 GM Canada began offering more axle ratio choices in Canada because cars were crossing both ways across the border.
Interesting that on 427 cars, if you got the higher horsepower you got lower gears than if you got the lower horsepower. I would have thought the 335 horse would have lower gears (because logic says it would need it)
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
The factory brochures list the following standard axles:
with 3 speed automatic:
250 or any 350 engine: 2.73
any 396 or 427 engine: 2.56
with power glide:
3.08 except 3.36 with wagon (no powerglide with any bigblock)
manual trans:
250 or 350 2bbl: 3.08 (except wagons or 4 speeds had 3.36)
350 4bbl or big block: all had 3.31 (except 3 spd manual 396 was 3.07)
This is amazingly restrictive by 60's GM standards. Also there were no regular production axle ratio options (code G90 or G94) offered. However special order axles were offered (code G95), but I don't have a 1969 Canadian power train chart to see what was offered. Generally speaking a special order option meant that the option should only be ordered by the dealer for a firm customer order as opposed to dealer inventory or zone production cars.
I asked on the Chevy side and there were RPOs for the other ratios, but I'm not aware of a way to have ordered them in Canada:
The 2.29:1 ratio was RPO GT2 & was only offered optionally on big block cars (396 & 427s) with Hydramatics.
The 2.56:1 ratio was RPO GT1 & was standard with the 396 & LS1 427 with the TH400. It was optional on all others when running a Hydramatic combined with engines ranging from the 250 six through the L48 350
The 3.55:1 ratio was RPO G96 & was offered with all engines optionally, though there were specific engine / transmission combos offering it
I'd forgotten that you for 2.56:1 with the "low rent" big blocks. What a steep ratio to saddle those cars with... at least they had a first great, I suppose, perhaps not much worse than my Powerglide w/ 3.07 anyway!
