i currently have 3.73's and am thinking of 4.10's.how much will 4.10's improve my 1/4 mile?1tenth2tenthsmaybee more?also will my top speed be greater due to me pulling a higher rpm in 5th,and last will my on the roll performance say 40-120 be better?
4.10s wont make as big a difference as you think when coming from a 3.73. It will be some, which is good, but it wont make you say "Holy crap!!" Now a 4.10 swap from stock would do that. They will help you pull stronger throughout your speedometer, but will limit your topspeed as opposed to 3.73's. But if you are using your head you shouldnt be pushing your car to its top limits anyway...thats how you get killed.
$400? Are you going to do it yourself? The gears cost atleast $200 alone, and a shop who is going to do it "RIGHT" is going to charge at a minimum $300-$400. As far as how much it will knock off, Ive seen 2-3 10ths from other cars doing the same thing. But who's to say they launched the same each time.
LOL I got mine installed for 500.00 that included a complete replacement of all bearings also adn teh gears. Try gefracing for the gears 139.00, also if you want to spray then run a 28" tire instead of 26" and you should be fine