03GT5spd

ok so i have a 03 gt 5spd when i bought the car it already had a stage 2 clutch and a short thro i think it might have gears but im not certain compaired to my dads 89 5.0 it feels like it but i knoe they came with gears compared to the 5.0 i have put trick flow underdrive pulleys on it and have been happy with it so far but last time i raced my brother inlaws ws6 trans am at about 90-100 he creeped past me since then i got a diablo predator tuner but havent raced him yet so i just ordered yesterday trick flow 75mm throttle body trick flow elbow plenum also 75mm and a cold air intake k&N so my question is how much power will i gain from the new mods plus the tuner and will he still creep past me at higher speeds if so is that cause he is a lighter car and more power and taller gears ?

jRock617

Even with your new mods, the LS1 will take you up top. They put down more power, and have a better head design for better airflow.
Get some headers, a mid-pipe, and cams (not cheap) and make sure you're running a better gear than stock; then you'll have a better chance at keeping up. what's your RPM in 5th gear at 70mph?

ct_white_stang

You won't really feel the difference beside the improved throttle response. The WS6 has got more power.

03GT5spd

yea so i just ran it down the freeway and at 70 mph in 5th its rite at 1400 isnt there another way to check gears? ive herd if u jack up the back end and spin the drive line 10 times however many times the tires spin is youre gear ratio well it will give u an estimate of ure gears

jRock617

from the sounds of it, you have 3.27s, stockers.

cliffyk

If you are running stock size tires (25" or so diameter, 810 revs/mile), then the speedometer must be incorrectly calibrated, or the indicator needle of either the speedometer or tach (or both) are improperly placed.

5th gear in an '03 is a 0.62:1 ratio, so with the stock rear-end gears (3.27:1), at 1400 rpm the tires will be turning 1400/(0.62*3.27) = 690.5 rpm. 690.5/810 = 0.852 miles/minute = 51.2 MPH...

This is the math behind my How Fast Can I Go in each Gear? calculator.

To be going 70 at 1400 RPM (if the speedo and tach are correct) the rear end gears would have to be:

Tire rpm at 70 MPH = (70/60) * 810 = 945 rpm;

This would require an overall gear ratio of 1400/945 = 1.48:1;

So since 5th is 0.62:1 the rear-end would have to be:

1.48/0.62 = 2.39:1?

I am not aware of any 8.8" gearset that is that high (numerically low) a gear, and you'd need 32"+ tall tires to be going 70 @ 1400 rpm with the stock rear-end gears.

The speedometer and/or tachometer must not be right...