I'm a new member here, I have lurked a long while before deciding to buy a stang. Yesterday I picked up a Race Red 2012 Mustang
GT Premium. It's got the Brembo package on it, and the previous owner (unknown to me before test driving at the dealer) put on Borla's Axleback exhaust, I'm not sure which one, its loud so I'm guessing it's the ATAK exhaust. Onto my question, I cannot find the rear diff listed anywhere and from what I can find, the stock rear gear is supposed to be 3.31, but I have seen a few places say 3.15. It is a 6spd manual so from what I can tell it has the MT82 transmission. I've modded cars in the past so I'm not a stranger to turning wrenches and the like, however this is the first RWD car I've owned and I know nothing about changing the rear gears.
I want to put 3.55 gears in, but I am not sure how to tell what I have, and how do I go about swapping the rear gears. I read if you are ~30k miles then you should replace the bearings too, my car has 16k miles on it so I don't know if I should be really worried about that. If I don't what could happen? Also does swapping rear gears void a factory warranty? I would appriciate any help, I have been searching all over but cannot find a consistent answer. Even if you guys just link me some reading anything will help.