Gene K

Im in the process of ordering a new 2011 GT and am a bit confused on rear axle ratio. On the 2005-2010 cars Ive heard the installation of 4.10's ruins them for autocross (Makes second to low). With the transmission change Im confused.

MPH at rpm limiter in 2nd (2.43)
2011 GT 3.31 (7000) 68
2011 GT 3.55 (7000) 63.5
2011 GT 3.73 (7000) 60.5

MPH at rpm limiter in 3rd (1.69)
2011 GT 3.73 (7000) 87

So I guess my question is would the 2011 GT work best with 3.31 run in 2nd or 3.73 run in 3rd?

Clif Brohn

3.73 would be better. You would need a mighty mean autox car to run anywhere near 87 mph, and even with 3.73s you'll find most of your work cone dodging is going to be getting done in 2nd gear

jayel579

Actually 3.55 would probably be your best option, you will never need to go beyond 2nd gear. It ultimately comes down to tires. If you run a shorter tire on a 3.73 ratio you very well could end up back at a 4.10 ratio. I run a 275/40r17 tire on my 2006 with the stock 3.55 rear, which gives me, I think, about a 3.90-ish ratio. My max-Q software has me topping out 2nd gear at around 67-68 miles per hour.

Gene K

Thanks for your input about the correct gears for autocross in a 2011 GT. However I want to make sure you didnt miss one important detail. 2nd gear is 2.43 compared to your 2.00

3.55 x 2.00 (2005) @ 6250 rpm = 68.77 mph
3.73 x 2.00 (2010) @ 6500 rpm = 68.34 mph
3.31 x 2.43 (2011) @ 7000 rpm = 68.26 mph

Rear Axle Ratio for same RPM in 2nd:
2011 / 2005-2010
3.31 = 4.02
3.55 = 4.31
3.73 = 4.53

Rear Axle Ratio for same rpm 3rd in 2011 vs 2nd in 2005-2010
3.73 (3rd) = 3.15 (2nd)