i have a 69 Skylark GS 12 bolt. Can't find anything on the outside axle housing.Pulled the rear cover and got this off the ring gear 14A39 GM CY 127 1. Is it a 2:78? That's what i come up with by dividing 39 by 14. The GS book i have doesn't even show a 2:78 gear ratio. From what i understand if the car had a 12 bolt, it was Canadian built. Thanks for any help or info. Tom
2.78 was a common ratio in the years '64-67. This is based on a Cdn. GM parts book. I don't know rear axles too well. No mention on bolt holes in these years. Was the car Canadian built or only the axle? Possible the gears were changed at some time?
I did not realize that they put 12 bolts in Skylarks from Canada. GS's, yes, but Skylarks too? The standard rear was 2.93. My 69 Canadian built GS actually has 3.08's. I understand many Canadian built GS's had the 3.08's as the standard fare. Weird, but apparently true. As for your 2.78's, knowing GM and all the other auto makers back in those days, absolutely anything could be possible. :Smarty:
Checked the book again. Cdn. built cars in '69, Skylark or GS, were available with the following ratios: 3.07,3.31,3.55 & 3.73. 2.78 was used only from '64-65 & 66-67. Like Ken stated earlier, anything is possible.
Just Count To get the ratio diviide the number of teeth on the ring gear by the number teeth on the pinion if it is 39/14 its 2.78
Have never ran across 2.78 ratio gears for a Chevy 12 bolt car carrier. 12 bolt 2.73's, I've chunked probably 40 sets, but never even heard of 2.78's. One thing I've noticed about the Pontiac cast 12 bolts housings ('70-72 455 useage) & the only '69 "Canadian 12 bolts" I've ever ran across, is they do not have a date cast in the rh lower diagonal webbing of the 12 bolt housing, like a Chevelle 12 bolt housing. Instead the date is cast underneath the housing on the "lip" facing towards the front. Hope this helps, Roger
Rodger, it really doesn't make any sense. The vin shows an H which makes it a Flint built car with a 12 bolt. Any thoughts other than the rear was changed? I was told the motor wasn't original, don't know why the seller wouldn't say anything about the rear. It sure looks original. Thanks Tom.
The thing is that if that rear was replaced 10 or 20 years ago, it probably does look original. o No:
