ok i looked it up the code is Gu2 so i have the 2.73 rear diff is that bad? or just slow? is it woth upgrading?

It's the highest gearing that comes in a 10 bolt. Yes, it's worth upgrading.

i am new what would you suggest upgrading to? and what will that do for my performace and gas mileage?

3.73

Up Performance, Lower Gas Mileage

3.73's are nice, but even a 3.42 is a decent step up. Quite often you can find an ENTIRE 3.42 rear end for cheaper than having the parts installed.

That's what I did, I had 2.73's and bought a complete 3.42 rear from a friend upgrading his M6 to a Strange 12 bolt. Gas mileage hasn't suffered too much, even with my converter - speaking of TC's - another option is to keep the 2.73's and get a TC.

3.73 automatics love it youll start to have problems with traction but your car will shoot out of the hole a lot harder.definetly a good upgrade for autos's

I say get a a torque converter and see how it feels. Then maybe get the 3.42's or 3.73's

I would be cautious about buying an entire rear end out of a M6. Especially somebody who is upgrading to a 12 bolt. You could run into problems if the last person beat on it.

My 3.42 geared, St3500 Yanked car went 12.15. 3.42s and a converter work very well together for an all purpose machine.

i think it depends on what you are using the car for. i have 273's and love them. my car is a daily driver, and i am not too much concerned with the gas mileage but on the highway they cruise. awesome pull in 3rd gear !!

i had my car at the track at pulled a 1.992 60ft with a stock trans,273s and street tires. not too shabby

I sold my complete 3.42 rear for $250, that's the way I would go in your situation if you can find one in your area (pretty heavy for shipping).

Rich