Gears for a turbo car
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Joined: Oct 2007
Posts: 604
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From: Gainesville FL
Gears for a turbo car I am building a 408 9.5-1 cr with a s480 turbo with lsa ported heads.I want to know what gear would u run with this combo.My car is a 99 transam with a t56 . I was planing to buy a new rear end when this one died ,and wanted to know what u all would use ...Thanks
Despite having a cam that called for a minimum of 3.73 gears, we did the swap and turned the car in to the most terroristic animal you could imagine on the street. The taller gears let the turbos spool quicker (or so it seems) and acceleration was improved across the board.
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I had 3.08's in my car when it had a 3200 stall and 26" tires.
On the street it was an animal. The 3.08's worked like lower gears do on a diesel allowing the turbo to spool way down low from the loss of gear reduction. It seemed to make it pull forever and ever and ever in each gear. Great for highway roll racing and 1/4 mile back half numbers. Not so good for 1/8mile and hitting the tires hard.
I swapped to a 3800 converter and 3.55 gears with the same size tire and the car is a whole different animal. Instead of having a smooth linear feel and like the car will never quit pulling with the 3.08's, it now with the 3.55's and higher stall is like a caged beast being unleashed when the pedal is pressed. It lights the turbo's just as quick but when boost comes on, it hits so much harder that it will annilihate the tires in 2nd at 45mph from a roll now where it wouldn't before.
In the 1/8th with the 3.08's I was either going through the traps on the limiter in 2nd or shifting literally 20' from the traps into 3rd killing my e.t. and mph. The 3.55's put me in 3rd about 200' out from the traps and 6200rpm in 3rd.
With a 26.5" vs. my 25.7" tires I use in the 1/8th I was able to run it out the back door at 6700rpm at the traps. With a 28" tire it would be right at 6500rpm where I want it.
With all that said I do wish I had gone with a 3.42 gear instead of the 3.55. It's splitting hairs now, but it would help with mpg just a little bit and now I trap 140 in 3rd with the 26.5" tire and 142-145 with the 28" tire and probably 135-137 with the 25.7" tire. You will have to do some calculations to figure out which will work best for you.
But as other's have said a 3.50 gear is a good all around turbo gear for both 1/8 and 1/4 and street. Especially with a 6 spd.
On the street it was an animal. The 3.08's worked like lower gears do on a diesel allowing the turbo to spool way down low from the loss of gear reduction. It seemed to make it pull forever and ever and ever in each gear. Great for highway roll racing and 1/4 mile back half numbers. Not so good for 1/8mile and hitting the tires hard.
I swapped to a 3800 converter and 3.55 gears with the same size tire and the car is a whole different animal. Instead of having a smooth linear feel and like the car will never quit pulling with the 3.08's, it now with the 3.55's and higher stall is like a caged beast being unleashed when the pedal is pressed. It lights the turbo's just as quick but when boost comes on, it hits so much harder that it will annilihate the tires in 2nd at 45mph from a roll now where it wouldn't before.
In the 1/8th with the 3.08's I was either going through the traps on the limiter in 2nd or shifting literally 20' from the traps into 3rd killing my e.t. and mph. The 3.55's put me in 3rd about 200' out from the traps and 6200rpm in 3rd.
With a 26.5" vs. my 25.7" tires I use in the 1/8th I was able to run it out the back door at 6700rpm at the traps. With a 28" tire it would be right at 6500rpm where I want it.
With all that said I do wish I had gone with a 3.42 gear instead of the 3.55. It's splitting hairs now, but it would help with mpg just a little bit and now I trap 140 in 3rd with the 26.5" tire and 142-145 with the 28" tire and probably 135-137 with the 25.7" tire. You will have to do some calculations to figure out which will work best for you.
But as other's have said a 3.50 gear is a good all around turbo gear for both 1/8 and 1/4 and street. Especially with a 6 spd.
i have 4.86 gears(31inch tire) in my car and best 60 with my 4.8 engine was 1.41 not great
leaving off the tranbrake, with a 2.75 first gear th400, it would hit full boost in 0.5 secs
leaving off the tranbrake, with a 2.75 first gear th400, it would hit full boost in 0.5 secs
3.23's here. It would depend what the car is being built for. The good thing is that you have plenty of options available to choose from... the bad news is which one?
For me, I kept the 3.23's as it's not a dedicated drag car.
For me, I kept the 3.23's as it's not a dedicated drag car.
We swapped the stock 3.42 in my buddy's 00 Vette for a set of 2.73s, after realizing that his 786 rwhp/700 ftlbs TT/346 combo did not work so well at lower speeds with the steep gears.
Despite having a cam that called for a minimum of 3.73 gears, we did the swap and turned the car in to the most terroristic animal you could imagine on the street. The taller gears let the turbos spool quicker (or so it seems) and acceleration was improved across the board.
Despite having a cam that called for a minimum of 3.73 gears, we did the swap and turned the car in to the most terroristic animal you could imagine on the street. The taller gears let the turbos spool quicker (or so it seems) and acceleration was improved across the board.
Unless you like shifting way too much
