I'm going to instal the 3.73 set on my 2004 GT 5 speed. My question is: Can i do this at any shop or by myself, or does it need to be done by a pro??
Is it just as easy as replacing stock gears with stock gears or does it need a different installation method?
Gear installation is not usually something you install yourself, unless you've done it before. Since you really don't want to mess up gears, it's better taking them to a reputable shop to get them installed.
if you dont know then dont bother. it isnt worth tring if you have never shimmed a pinion and carrier before. if you can do it at a shop with someone who can help that really knows how to, that would be the easiest way to go. its a pain in the a$$ and you have one try to get it done right. wrong even by the slightest shim and you will have a rear that howls and whines.
I wouldn't attempt it yourself. A shop will have all the special tools you'll need.
Your gonna love the gears though. I couldn't decide between 3.73s or 4.10s so I went in the middle and got 3.90s
I'll agree with the other guys. If you don't know what you're doing, do not try it. Changing gears isn't like changing spark plugs. There are so many little things that have to set just right like backlash and pinion depth that if you're even a fraction of an inch off, you'll throw the whole setup off and ruin the gears. Basically put, if you don't know what you're doing, let someone who knows how to do it do it for you.