jlt31971

How can I tell if I have the 3.55 or the 3.73 rear end. Also I wana switch to 4.10s is it as simple as a ring and pinion gear or is there more to it. Car is a 06 GT convertible with a 5 speed, gt500 wheels and tires, cai and catback exhaust with tune (for now supercharger is in my future).

Misbehavin

If the rear end is stock, there should be a sticker on the housing that indicates your gear. A 2006 GT didn't come stock with 3.73, unless it was a Bullitt. Autos were 3.31, and manuals were 3.55. There's also a door sticker that will indicate the gear ratio. I think it was "CD" for 3.55, and "CG" for 3.31. That may have changed in more recent years, but I believe that applies to 2006.

If you suspect the rear gears have been changed, you need to raise the rear of the vehicle. Mark the driveshaft, and turn the rear wheels once while noting how many times the driveshaft turns. A 3.55 should spin the driveshaft 3.5 turns, while a 3.73 will spin the driveshaft about a quarter turn more. It can be a little tough to tell the difference between them due to the small difference.