This is a track only car. What kind of gains can I get????

 

A4? M6? Doesn't really matter I guess, but I'd say 4.10's / 4.11's are probably a better choice for a typical 4th-gen, since the tire height is normally around ~26". Now if you've got a crazy motor that screams out to ~7000 rpm, and if you want to run a slight taller tire, then you could run a 4.56 and do ok, but I'm not even sure if there are 4.56's built to fit the stock 7-5/8" 10-bolt?

 

Not near enough info to make any intelligent answer. How high does the motor rev, what size tires are you using, and what are the expected trap speeds,etc.???

 

With what little (no) info you gave I am going to assume you have the stock 10-bolt. I would go with the 4.11s and then while you are at it order a Strange 12-bolt with 4.11s in it as well ... seeing as how the 10-bolt (again guessing this is what you have) is going to last a couple of launches and then crap out on you. It just is not made for launches, which it sounds like you will be doing a lot of. The 4.10 and 4.11 ratio are about the best for our cars. The 4.11 is just slightly ahead of the 4.10 due to the fact that the 4.11 has one less tooth which means the other teeth are thicker....ie stronger!!!

 

Obviously, to answer in a meaningful manner, you need to tell us:

Engine peak power RPM and redline RPM
Anticipated trap speeds
Trans type and gear set, do you plan to finish in 1:1 ratio?
Convertor slip if an automatic
Tire diameter, and estimated growth at trap speeds
Type of racing - 1/4-mile, 1/8-mile, something else
Rear axle type - 10-bolt, 12-bolt, 9-inch

 

Sorry for the lack of info and the slow response. I have been out of town. I will be useing a 700r4 with a 4000 stall. 2.5str. 9'' rear. I hope to trap at 125-130 spraying. I also plan on useing a 28'' tire in the 1/4-mile.