tacklebox

iTrader: (10)

I tried posting this over in the drag racing forum, but no one seemed to know. This is a copy & paste of my other thread:

I have an N/A heads cam 6 speed car. Right now i have my stock rear with 3.42's in it. I just got my Fab 9" delivered friday, which has 4.11 gears. I realize taller gears are meant to get you down the track quicker, but do they affect mph much? Will I gain +1 or 2 mph or even more, or see no difference at all?

MattIROC

iTrader: (19)

It'll be the same, or it may drop 1 mph. You shouldn't see a mph gain.

tacklebox

iTrader: (10)

Anybody else?

01ssreda4

iTrader: (96)

if it accelerates quicker down the entire length of the quarter shouldn't the trap be higher???

Kevin97ss

You need to give up some more info.

At what RPM does it cross the finish line with the 3.42's? and in what gear.

Where does your engine make peak power and peak torque?

Are you using a bias ply tire or radial?

tacklebox

iTrader: (10)

Cross finish line @ maybe 4500 rpm in 4th gear w/ 3.42's going 118-119 mph. Peak hp @ 6200, peak tq @ 48-5300. Tires are 275/50/15 MT ET street radials.

wrd1972

iTrader: (12)

If you are crossing the line at 4500 RPM in 4th, then there is a lot being left on the table. You want to be crossing the line slightly above your peak horsepower and in your case about 6300 RPM. This will give you the best times and MPH.

You will definitely see better MPH with the 4.11's.

Kevin97ss

4.11 should work great and put you just above peak power crossing the line, right at 6300rpm @ 119mph. I'm guessing it can rev to 6500? Hopefully so as it should pick up 1-2mph and 2-3 tenths, assuming you can stick the launch.

The 3.42 you have now work out to be about 5250 rpm crossing the line @ 119mph.

tacklebox

iTrader: (10)

Yea i can rev to 6800. Hoping to pick up a little more than 2-3 tenths cause now i can launch hard also. No more 1.8 60's for me i hope.

LS1>girlfriend

iTrader: (19)

i picked up 2 mph going from 3.42 to 3.73.

silverz28camaro

iTrader: (20)

I have always like 3.90 gears for the 6 speed cars, seen a lot of great gains, not mine but friends times.

here are mine:

2000 auto z bolt on car best mph with 2.73's 109,swaped for 3.73's 110, also a .4 reduced et.

my 88 dodge ram with 3.21 gears was 16.1 @ 83 swapped for 3.90's and went 15.6 @ 84