3.55 in my v6?

well to answer your questions I have 373 rear gears in mine and I love them but mine is a 5 spd I installed mine in my garage and doing them was not hard and it was my first time doing gears they came out perfect . The reason I did mine is because the average cost to have them installed is 250 to 300 thats not including the cost of the gears and traction lok unless you buy the parts yourself another thing to remember most shops dont give you any kind of warranty on performance parts. As far as voiding your warranty im pretty sure any time you add any performance aftermarket parts your warranty will be void . usually when it comes from the factory I think they mark it in someway to know if you crack the differential im not sure on that so don't quote me . Alot of ppl go 373 with a 5 spd and 410 with the auto so consider that as well . good luck with your decision

False. They can't void your entire warranty because of an aftermarket part. They can only refuse to make the repair under warranty if they can show that what you added caused the problem.

Hi KisStang,

This is Deysha with Ford Customer Service. arcwcb is right, an aftermarket part will not void your warranty. However, if a specific aftermarket part causes a concern, that specific repair will not be covered. You can refer to your Warranty Guide on page 13 for further info.

Deysha
Ford Customer Service Division