Gear Selection
 

Need advice on gearing....Car is a C5 'Vette, M6 manual trans, roughly 1,100whp, 28" tire. I am wanting to go 8.90 - 9.0. I currently have 3.90 gears and with those gears I could theoretically hit 160mph @ 7500 RPM. Should I keep the 3.90s or go with 3.73s which theoretically give me 167 at the same RPM. Or should I go lower than 3.73s.

If you have 3.90's then you are lower than 3.73. If you mean lower numerically like a 3.54 then, that would be geared higher or taller. Get a Moroso power speed calculator or get an app for your phone, those things have every tire size-gear-rpm scenario, you'll probably trap in 4th gear which is 1:1 and that's what those things are based on. IMO, you have the right gear now. Does your car have a cage? Youll be asked to leave if you run a big mph like that and you don't have one.

a cage isn't gonna happen this year unfortunately. gotta get the trailer built first so I can drag the car to Houston with me in Nov. Will probably do a few track rentals this year to work on my car and a few other cars.

I would run it with the gear you have to see where you are before changing anything.

An 8.90 ET should only take around 153 MPH or so on a well sorted car. Unless you have to run lower boost in the lower gears, then it may be getting up towards 160 MPH.

Al

Have you upgraded that c5 rear or is it stock with 3.90. I don't remember those rears even upgraded being able to handle that kind of power. Ive seen most go to the c6z06/zr1 style rear but you only have a the option of the 3.42.

Why not go even lower than 3.73? Numerically. I doubt your car needs more gear for the launch. To put it in perspective, my car hasnt even made 1000 yet, is on a 28" tire, and has a 3.50 gear, and I have cut a 1.25 sixty foot before.

3 rib diff with C6 Z06 internals and a trans/diff brace. I only really need it to hold together this summer, next year it gets a 9" SRA conversion with a 4 link