71 Lemans will mostly be driving I’m town. I’d like to have a little fun at the stop light from time to time, and the stock gear with one -wheel -peel isn’t cutting it. This is a auto 3 speed car. Anyone have suggestions? I’ve heard 3:55 from a few of the GTO guys locally, but will the 3:73 give me a bit more get up without extreme highway rpm?
3:73 vs 3:55 gears. Big difference?
- Thread starter LeGrind
- Start date
cammerjeff
Well-known member
FYI
I am assuming you have a 8.2 rear axle, keep in mind that 8.2 BOP (Buick/Olds/Pontiac) are about the most expensive rear axle to change ger ratio's on. It usually will end up costing you at least $1000 to properly swap out the ring and pinion (if you have a shop do it for you.) and ratio's are a bit limited.
The BOP ring and pinion alone is about $450, the rebuild kit is around $250 so you are already at $700 without Labor and any oil, and that is if you can reuse your current carrier, if you can't and have to either purchase a different series carrier you are looking at another $500. Or a ring gear spacer kit with longer bolts at around $150.
I am assuming you have a 2 series carrier with somewhere around 2.73 to 3.23 gears at the moment? If you do the 3.55 or 3.73 will not work with your current carrier without at least a ring gear spacer kit.
Now I agree that a rear gear swap is about the quickest and easiest way to get more acceleration out of a 70's car as most have 2.41-3.23 rear gear ratios. I would check to see what you actually have 1st, if it is a 3.23 it would not be the 1st thing I changed, if it is a 2.41-2.73 I would seriously look into the swap.
Also before buying any parts make sure what rear axle you have in the car. It could have been built with a Chevy or BOP 8.2 ten bolt, a Chevy or Olds 12 Bolt. Or anything could have been swapped in during the last 50 years. All the axles I mentioned take different ring and pinnion and rebuild kits. At various prices and availability.
I am assuming you have a 8.2 rear axle, keep in mind that 8.2 BOP (Buick/Olds/Pontiac) are about the most expensive rear axle to change ger ratio's on. It usually will end up costing you at least $1000 to properly swap out the ring and pinion (if you have a shop do it for you.) and ratio's are a bit limited.
The BOP ring and pinion alone is about $450, the rebuild kit is around $250 so you are already at $700 without Labor and any oil, and that is if you can reuse your current carrier, if you can't and have to either purchase a different series carrier you are looking at another $500. Or a ring gear spacer kit with longer bolts at around $150.
I am assuming you have a 2 series carrier with somewhere around 2.73 to 3.23 gears at the moment? If you do the 3.55 or 3.73 will not work with your current carrier without at least a ring gear spacer kit.
Now I agree that a rear gear swap is about the quickest and easiest way to get more acceleration out of a 70's car as most have 2.41-3.23 rear gear ratios. I would check to see what you actually have 1st, if it is a 3.23 it would not be the 1st thing I changed, if it is a 2.41-2.73 I would seriously look into the swap.
Also before buying any parts make sure what rear axle you have in the car. It could have been built with a Chevy or BOP 8.2 ten bolt, a Chevy or Olds 12 Bolt. Or anything could have been swapped in during the last 50 years. All the axles I mentioned take different ring and pinnion and rebuild kits. At various prices and availability.
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Ok great, thanks for the info! I just finished my first rear end swap in a C10 and it went good. Went with posi and 4:10 gears. What a difference! I’m glad I did that one first, because I will definitely be going with the 3:55 in the Lemans. I will Jack the car up today and investigate current set up. As far as I know it’s stock.