DylanFan

Yesterday I bought a Tungsten Grey 2007 GT Deluxe with 6 Spped Manual, Shaker 500 and Interior Upgrade Package that has 3,600 miles. The salesman said the guy had "special gears" but didn't say weather he ordered it with "special gears" of if he had them installed after purchase. Last night while driving the car it didn't feel like it was going as fast at the speedometer was reading. Today my wife brought her GPS that tells how fast your car is moving and the speedometer was reading about 3 MPH faster than the GPS said we were moving. When the speedometer said 60 the GPS said 57. Could this mean gears were installed without the computer being reset for new gears? It doesn't seem like a big enough difference for a gear change. Any thoughts? Could I take it to the dealer and have the speedometer calibrated? Otherwise I love the car. The car still has 2 years of factory warranty left and of course over 32,000 miles on the warranty.

Argonaut

6spd? Thats a new one. If its truely a 6sp then someone did a tranny swap.

In 2007 the stock gears were 3.31 (I think thats the right one) and the option was 3.55. Common aftermarket are 3.73 and 4.10. Yes a gear swap can throw off your speedo, as can a change in diameter of your tires, and yes its possible you have the aftermarket gears and the computer was not updated. But, the speedos in these cars have a reputation for being a bit off and 3mph isnt much. If you want to try and figure out exactly whats going on, use one of the calculators at the following website. You can plug in diameter and RPMs and the above gears and it will tell you what the speed should be. http://www.wallaceracing.com/Calculators.htm

rugedraw

Jack up the back of the car completely and leave it in neutral. Make a mark on the drive-shaft, and give it a full 360 degree turn, and have someone count how many times the tires rotate in one spin of the driveshaft.

3 1/2 spins, you got the 3.55 gears. 3 1/4 spin, you got the 3.31s. 3 3/4 spins, you have the 3.73s. Over 4 spins, you got the 4.10 gears.

Then you can figure out how to recalibrate it. Instead of paying the dealer to do it, you are better off using that money to buy a tuner which can calibrate the speedo and give you some HP to boot!

DylanFan

Oooops, I should have said "5 Speed". Guess I was thinking of my wife's Corvette with 6 speed. When I started driving the GT I kept wanting to shift into 6th gear which would have been reverse. That must be why you can't shift from 5th to reverse.

Cuzzo

LOOOL i hope you didn't try that rofl