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Rear gear ratios


ejw71

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Dave & Leo seem correct.

I got a one-legger with 2:56's myself in my '70 SS454.

 

Dan

my 72 custom came with a 12 bolt with opt code g35 posi track and opt code g80 2.73 thats what was on my build sheet
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  • 1 month later...

Was reading the 1970 restoration booklet on rear gears. Quite lengthy but it lists the "standard" gear ratio for all of the power team configurations. Basically the pontiac rear was the 10 bolt and was only used on 350 2bbl cars. The ratio for a 3 spd manual = 3.08 and a 4 speed = 3.36 a powerglide = 3.08 and th350 = 2.73, 350 4bbl = 12 bolt rear, 4 spd = 3.31 powerglide & th350 = 2.73 400 2bbl = 12 bolt 4 spd = 3.31 and th350 = 2.73 402 4bbl = 12 bolt 4spd & th400 = 3.31 454 = 12 bolt th400 = 3.31 . According to the restoration guide there were 3 ratios available for the 10 bolt, 2.73, 3.08 and 3.36 and 3 ratio's for the 12 bolt, 2.56, 2.73 and 3.31 all ratio's for all rears were available with posi.

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there were many 70SS 454 cars built the 2.56 rear ratio i have a build sheet for a 70SS 454 with a 2.56 ratio , i have never seen a build sheet with any rearend other than 2.56-3.31 does anyone out there have a build sheet with any other ratio on a 70 or 71 SS ??????

 

Leo

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I was referencing the data that Chevy provided for the 1970 model year. Can't say about 1971 or 72. I know that higher numerical ratio's were available over the counter from parts department but the restoration packet includes the data that they provided to the AMA and the format that the dealers used to fill out the order sheet. Both only list the 3 ratio's each for 10 and 12 bolts. It would be interesting to see a build sheet with ratio's other than what the books say.

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build sheet lists GW4 - 2.56 ratio axle G80 positraction , see if i can scan it in Z20 Monte Carloss it is a baltimore built car fully loaded , i believe a lot of the 70 cars had this ratio

 

Leo

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Leo, you are correct that many cars had the 2.56 because it was one of the 3 available ratios. What would be unusual would be to find a build sheet showing a 3.55, 3.73 or 4.10 gear sets. All were available over the counter, because my 402 has 3.55's in it with a factory gm part number on the ring and pinion. However my build sheet and the code stamped on the housing confirm a factory delivery of 3.31's. I purchased the gear set because it was NOS and I wanted a bit more oomph off the line.

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  • 3 months later...

yep agree 100% i have never seen a monte any monte carlo with anything above a 3:31 from the factory

 

Leo

my 72 custom came with 2.73 posi 12 bolt it was on my build sheet
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This is getting interesting. My '71SS came with the 3.31 gears. I have seen Chevelles with all kinds of gears; 355, 370, 411, 456... But Montes built with big-numbered gears is rare? That seems strange.

I guess it fits with the end of the muscle car era, the prices of fuel, and the image of luxury that Chevrolet pushed on the Monte Carlo.

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  • 15 years later...

Hello all 😎

out of all the Monte Carlos I had back in the 70’s - 80’s 

2:73 common gear and sports 3:73 or 4:11/4:10

3:31 was in ElCaminos for the most part along with 3:55 gear   Rare but sometimes 3:73

i still hVe all my books from when my parents bought our 71 Monte new 

 

hope this helps

JP

 

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