usmcmp90

i have an 08 GT/CS and i'm looking to upgrade my gears to 3.73 but from i've heard there was 3.55 gear option for these cars but i have no idea whether mine has it or not as it was used. any1 know if theres someway to tell?

gman73

If you have 3.55s at 70 your RPMs would be just under 2100 RPMs assuming you have the 235/50/18 tires. If you have 3.31s, your RPMs would be under 2000 RPMs.

ski

A difference of approx. 100 rpm may be too small to detect on the tach. Suggest doing 70 mph in 3rd gear. 3.55's will spin the engine a little over 4300 rpm, and 3.31's a little over 4000 rpm. These assume your car is a manual.

bilbob2

Um guys isnt the stock gear ratio printed on the inner door on a sticker?

Goldenpony

I thought the ratio was on a metal tag on the rear end housing.

gman73

The sticker is printed on the pumpkin but the OP bought it used.

ski

Actually, it's in code: CG=3.31, CD=3.55

usmcmp90

thx for the info, i'll be taking a look in the morning

bilbob2

Someone just told me to put my car on jackstands, turn my rear wheels 1 turn, and the DS spins in correlation to the gears.

example 4.10's spin 4.1 times

Wonder why no one said anything on this thread about it yet?
Oh wait... would it be too hard to tell the diff of the spin on the DS between
3.55 and 3.73? My guess is yes to this and if so I feel really dumb now for posting this.

ski

You should be able to tell the difference between 3 1/2 turns vs. 3 3/4 turns of the driveshaft if you use chalk marks.
However, that method is labor intensive, and would probably be used only if the other easier suggestions do not produce an answer.