Great forum, thanks for all the info.
My first post, 2007 GT vert, manual trans, 3.31 rear gear. I installed the Whipple 500hp kit and love it. Was thinking of installing 3.73 or 4.11 gears for the fun factor. Anyway the tune supplied by FRP is for 3.31 gear. If I install higher ratio will this mess with the tune or just cause speedo error? I believe FRP will send a new tune for gear change (from what I have read, sure there is a charge involved) just wondering if there is any risk if I dont get the new tune right away (I can live with speedo error for a while). Thanks for your help.

 

For our axle there isn't a 4.11...there is a 4.10 tho (don't want you to keep saying it and get flamed later lol) I also have the HO kit and am wanting to re-gear the axle. What you could do is go to 3.73s and try those and if you want to go higher you can or you could go to 4.10s and if that's too high you could back back down. Most people will say 4.10s though just because of how hard they pull. Some people record little or no change in gas mileage with the 4.10s unless on the highway...and in fact one person recorded an INCREASE in mpg...have no clue how he did that though lol. I'm going to go to 3.73s if I ever change gears. Change your driveshaft first to a one piece aluminum driveshaft like the one from Spydershaft. It's a mod that nets you about the same gains at the gears and you won't have to worry about having them installed wrong, and the Driveshaft is about the same price as having the gears and then the gears installed (assuming you do your own install on the driveshaft that is)

 

I have 4.10's and will be getting the whipple h.o. kit installed beginning of next week. ill let you know what I think then!

 

Looks like traction will be an issue for many but the 4.10's are fun....I was thinking of going to that gear as well but the stock 3.55's already break traction in the first 3 gears! Later J IMO rear suspension mods and fat sticky DR's are in order for any one with the Whipple J

 

+1 lol I can roast tires through first and second and then a little in 3rd on the right road with the right temperatures lol[8D]I'd hate to have to launch this car without drag radials or slicks at the track with anything more than 3.55s...I have 3.31s and can only imagine how 4.10s are just calling for tire smoke

 

I dont believe you will have any other problems other than speedo error swaping gears on a Manual. Automatic yes, (just in case someone was curious.)

IMO 4.10 are too much with the whipple. It will only hurt traction more.

For a street car I would stick with 3.31 or 3.55's whichever came stock in your car.

I would defineatly add an Alum FW, and Alum D/S, as the lower rotational weight will help the motor spin faster and give a nice gain, similar to gears.

Now if you want big HP in the future or to track the car alot, I would get 3.73's. They are the best all around performance gear. Launching the car on slicks with the right suspension will be no prob. If you go this route I would change the diff at the same time to a Tru Trac or similar. You will need it anyway so might as well do it while its apart. Make sure you go to the best shop, not the cheapest. Mis-aligned gears will cause you lots of problems.

Good Luck