3.15 "Performance Axle" Question!
Thread Starter
Drifting
Joined: Nov 2001
Posts: 1,791
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From: NE PA
3.15 "Performance Axle" Question!
Does anyone know why the Corvette's (automatic-equipped car) performance axle is 3.15 when the F-Body performance axle on my A4-equipped '99 Camaro SS was 3.23? Why do they use a taller gear in our cars? Thanks!
Burning Brakes
Joined: Sep 1999
Posts: 1,247
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Re: 3.15 "Performance Axle" Question! (XTrooper)
Hi Steve,
Glad to see you follow the Vette forum. As to your question, this is just a guess, but here goes. The tire on the C5 (275-40-18) measures 26.6" in diameter, whereas the stock F-body tire, either the 245-45-16 or the 275-40-17 both measure 25.7". Now if you put this smaller diameter tire on the Vette I bet the rear end ratio may come out very close to 3.23. I know someone out there has the formula to figure this. Whattathink ? If I am correct then in actuallity they both have 3.23's.:)
BTW us C5 guys envy the fact of how easy (read CHEAP) it is to upgrade to 3.73's in the F-bodys. F-bodys-Parts&labor= $400-$500....C5 P&L= $2000-$3000:eek:
Mike:flag
(Turbo Mike C on LS1.com)
Glad to see you follow the Vette forum. As to your question, this is just a guess, but here goes. The tire on the C5 (275-40-18) measures 26.6" in diameter, whereas the stock F-body tire, either the 245-45-16 or the 275-40-17 both measure 25.7". Now if you put this smaller diameter tire on the Vette I bet the rear end ratio may come out very close to 3.23. I know someone out there has the formula to figure this. Whattathink ? If I am correct then in actuallity they both have 3.23's.:)
BTW us C5 guys envy the fact of how easy (read CHEAP) it is to upgrade to 3.73's in the F-bodys. F-bodys-Parts&labor= $400-$500....C5 P&L= $2000-$3000:eek:
Mike:flag
(Turbo Mike C on LS1.com)
Team Owner
Joined: Sep 2000
Posts: 25,004
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From: Far NW 'burbs of Chicago
St. Jude Donor '13
Re: 3.15 "Performance Axle" Question! (Mikie C)
Well, the tire diameter does not change the rear gear ratio, but it does change what your rpm will be at a given speed with the same ratio in the axle. If your tire diameter numbers are correct, the Corvette takes a double hit: the larger diameter tires on the vette will reduce your rpm at a given speed, and our 3.15 instead of 3.23 makes it worse. Even with the 3.15 I'm only doing 2,000 rpm at 72 mph, so I wouldn't hit peak horsepower until about 200 mph and redline at 216. So even the "performance" 3.15 is too tall, I'd go to 3.42 in an instant if it wasn't so much hassle.
The gearing is probably the biggest reason why the f-bodys run so well against the C5, even though they have more weight and slightly less power.
[Modified by Gearhead Jim, 12:19 PM 11/12/2001]
The gearing is probably the biggest reason why the f-bodys run so well against the C5, even though they have more weight and slightly less power.
[Modified by Gearhead Jim, 12:19 PM 11/12/2001]
Burning Brakes
Joined: Dec 1999
Posts: 1,121
Likes: 0
From: Atlanta GA
Re: 3.15 "Performance Axle" Question! (XTrooper)
Actually the taller tire on the vette has the opposite affect. 3.15s on a C5 would be like 3.00's on an F-body. I would guess that 3.42s on a C5 would be similar to 3.23s on an F-body.
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