1980 Corvette Gears
Thread Starter
3rd Gear
Joined: Oct 2012
Posts: 3
Likes: 0
1980 Corvette Gears
I recently purchased a 1980 Corvette Auto Transmission that has undergone a complete restoration. The previous owner took out the L48 and had it built to produce about 400 HP. He changed the gears to 3.73 from the original 3.08. The car has tons of power and torque, but at highway speeds of 70 mph it's turning about 3500 rpm. How much would the rpm drop at that speed if I went back to the 3.08 gears?
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
It would cost quite a bit more money, but a better solution would be to install an overdrive transmission. With the 3.73 gears, a 200-4r would probably be your best bet. To answer your question, I think my '80 'vette turns about 2800-2900 rpm at 70 with the 3.07 gear.
Keep the shiny side up!
Scott
Keep the shiny side up!
Scott
Drifting
Joined: Dec 2004
Posts: 1,714
Likes: 42
From: Austin Texas
There are many, but this is a calculator I play with for questions like this.
http://tri-5.chevyrides.com/rpm.ph
My car makes a little less power than yours. I went from 3.08 to 3.55 rear. My car also has a TH400 with a 2800 converter. I am about to swap out the transmission to a 2004R. It has an ever so slightly lower first gear and a much needed 4th gear overdrive.
Our 3 speed transmissions with the 1:1 end drive ratio can be limiting and make you choose top end speed or low end power based on your rear end choice.
You know how your car is crazy fun to drive off the line now? It won't be as fun with a 3.08. However, it would probably be a cheaper solution to your hwy cruise rpms to change the rear instead of the transmission. I bet you could find a guy with a Vette locally that would love to swap his 3.08's for your 3.73's.
http://tri-5.chevyrides.com/rpm.ph
My car makes a little less power than yours. I went from 3.08 to 3.55 rear. My car also has a TH400 with a 2800 converter. I am about to swap out the transmission to a 2004R. It has an ever so slightly lower first gear and a much needed 4th gear overdrive.
Our 3 speed transmissions with the 1:1 end drive ratio can be limiting and make you choose top end speed or low end power based on your rear end choice.
You know how your car is crazy fun to drive off the line now? It won't be as fun with a 3.08. However, it would probably be a cheaper solution to your hwy cruise rpms to change the rear instead of the transmission. I bet you could find a guy with a Vette locally that would love to swap his 3.08's for your 3.73's.
Thread Starter
3rd Gear
Joined: Oct 2012
Posts: 3
Likes: 0
Thanks guys, I appreciate the information. I know I would lose low end power from the switch to 3.08s, but it would be a better highway car. If he didn't change the speedometer gears for the 3.73 rear end gears, would the speedometer read higher or lower than the speed I am really traveling?
Race Director
Joined: May 2006
Posts: 18,734
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Higher, in order to drive at say 70 everything is spinning faster than before including the speedometer gear.
Not knowing your tire diameter though, 70 and 3,500 rpm sounds correct.
Not knowing your tire diameter though, 70 and 3,500 rpm sounds correct.
Last edited by MelWff; Oct 27, 2012 at 09:51 AM.
