808z28camaro

My buddy is planning on changing gears (10 bolt) on his m6 from stock 3.46 to 3.90. how critical is re-tunning the ecm to run the 3.90 gears. is it only speedometer calibration or does it affect the actual tune/performance of the car? He said he doesnt care if his speedometer is wrong.

I have no idea how important it is to tune or not. my car was custom tuned by a shop after my rear was installed along with other mods.

Any help will be appreciated. thanks

FirstYrLS1Z

iTrader: (4)

Since it's M6,speedo calibration only.

808z28camaro

perfect. cool. thanks!!