Upgrading Gears question
Thread Starter
Former Vendor
Joined: Nov 2005
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From: Spring Texas
St. Jude Donor '08
Upgrading Gears question
Does the overdrive gear remain the same ratio to the wheels? I'm looking to maintain good highway fuel economy for crusing, but the idea of more low end torque makes me go 
Le Mans Master
Joined: Mar 2002
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From: Mississauga, Ontario Corvettes were built to be driven...not trailered
St Jude Donor '07-'08-'09
Not sure of the exact numbers but I rev at about 2600 RPM at 70 MPH (used to rev about 2400)...I may have lost about 1 mpg but still running about 27.5 mpg with 418 at the wheels
Le Mans Master
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From: Mississauga, Ontario Corvettes were built to be driven...not trailered
St Jude Donor '07-'08-'09
Thread Starter
Former Vendor
Joined: Nov 2005
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From: Spring Texas
St. Jude Donor '08
Has anyone upgraded from the 2.73 to 3.15 gears? It seems to be a buyer's market with all the 3.15 cars upgrading to the 3.42s. I'm not trying to build a race car, I just want sometihng that won't embarass me on the street. here's what 'm thinking:
Mike-Mercury's TC: ~$200 (possibaly $180 for rebuilt)
3.15 gears: ~$375-400
Installation ~$400-500
If i can get this done for $1000, I'll be extatic. I'm not sure if my OEM parts are worth anything though.
Mike-Mercury's TC: ~$200 (possibaly $180 for rebuilt)
3.15 gears: ~$375-400
Installation ~$400-500
If i can get this done for $1000, I'll be extatic. I'm not sure if my OEM parts are worth anything though.
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Race Director
Joined: Dec 2004
Posts: 13,760
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From: Haymarket VA
Has anyone upgraded from the 2.73 to 3.15 gears? It seems to be a buyer's market with all the 3.15 cars upgrading to the 3.42s. I'm not trying to build a race car, I just want sometihng that won't embarass me on the street. here's what 'm thinking:
Mike-Mercury's TC: ~$200 (possibaly $180 for rebuilt)
3.15 gears: ~$375-400
Installation ~$400-500
If i can get this done for $1000, I'll be extatic. I'm not sure if my OEM parts are worth anything though.
Mike-Mercury's TC: ~$200 (possibaly $180 for rebuilt)
3.15 gears: ~$375-400
Installation ~$400-500
If i can get this done for $1000, I'll be extatic. I'm not sure if my OEM parts are worth anything though.
Do it!
Team Owner
Joined: Sep 2001
Posts: 23,283
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From: Lake Elsinore, CA
To answer your question: No - the final drive ratio in each gear changes when you swap to a new diff ratio, including the overdrive gear. The final drive ratio is a function of the gear the tranny is in at any one moment and the diff ratio. It's a fixed mechanical relationship. The power is transmitted through the tranny gear set and then the diff gear set. When you change the ratio in the diff, the resulting final drive ratio in each gear is changed accordingly. In the case of switching from 2.73 gears to 3.42, the rpm's are increased 25% in each gear.
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Team Owner
Joined: May 2005
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From: Flagstaff Az.
I had 3:15s and changed to 3:42's. I added a Yank 3500, heads ,cam, and some other stuff and mileage dropped from 31 to 28 at 75-85 highway cruising. Since a lot of the 6 speed guys are changing to lower gears, there are some 3:42s available a good prices. 
Thread Starter
Former Vendor
Joined: Nov 2005
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From: Spring Texas
St. Jude Donor '08
It's more of a question of availability and price. The 3.42 gears seem to be $200-300 more expensive than similar condition 3.15 gears....plus it would allow me to keep some top end.
If i happen upon a 3.42 bargin, I will certainly consider it.
Le Mans Master
Joined: Mar 2002
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From: Mississauga, Ontario Corvettes were built to be driven...not trailered
St Jude Donor '07-'08-'09
If you want to swap out just the gears, I'm not sure you can do that. Unless things have changed, you can't go from 2.73's to 3.15's using the same "Pumpkin" (the 2.73 housing is too small)...you would need a whole new rear housing for the 3.42's
(you can go from factory 3.15's cause they used the same housing as the 3.42's)
(you can go from factory 3.15's cause they used the same housing as the 3.42's)
Thread Starter
Former Vendor
Joined: Nov 2005
Posts: 8,995
Likes: 2
From: Spring Texas
St. Jude Donor '08
If you want to swap out just the gears, I'm not sure you can do that. Unless things have changed, you can't go from 2.73's to 3.15's using the same "Pumpkin" (the 2.73 housing is too small)...you would need a whole new rear housing for the 3.42's
(you can go from factory 3.15's cause they used the same housing as the 3.42's)
(you can go from factory 3.15's cause they used the same housing as the 3.42's)
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St. Jude Donor '12-'13-'14
Le Mans Master
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Posts: 5,300
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From: Mississauga, Ontario Corvettes were built to be driven...not trailered
St Jude Donor '07-'08-'09
Actually, thats not a bad all-in price...and yep, you would have the option of putting 3.42's down the road in the 3.15 housing
