changing gears 343/373
#1
03-27-2006, 05:06 PM
changing gears 343/373
looking at my purchase sheet , it says i have a 343 rear gear, i am thinking of going to a 373. my question is , will i notice a big difference in performance, or is this not enough and i should go to a 393 if they make it. i have a 6 speed manual. how much will i lose on top end. i dont need to go 175mph but would like to stay around 160mph in 6 gear.
#2
03-31-2006, 01:41 AM
RE: changing gears 343/373
You will notice a big difference if you move up to 3.90s or 4.10s. Although I have not done this (I plan on getting a supercharger one of these days), I know many people who have and they say it is like getting an extra 50 HP. The 390s are a good choice f you like doing the 1/4-mile. You can actually see a .5 second improvement over the 3.42s. I'm not sure about top speed, but I'll be 160 is attainable.
#3
03-31-2006, 09:38 AM
RE: changing gears 343/373
Moving to a 3.73 from a 3.42 gear ratio is a 9% increase in gear leverage, so it will make a noticeable difference in initial acceleration, equal to adding about 35 ft lbs of torque. It will cut about .2 sec off the quarter mile time but make little difference in your trap speed.
The 3.73 will reduce your speed at the red line in each gear by 9%, so top speed of a C5 being about 175, that will fall 9% to 160: you will just barely have what you want. It will also increase the top speed the car will pull in 6th (it will only pull about 140 stock) to about 150 (5th will still be the highest speed gear but not by much).
A more significant consideration is that your car will rev 9% higher at every speed in daily driving (you will notice the difference).
Ecklers sells a very strong 3.90 rear end which will make even more of a change, cutting .4+seconds off your quarter mile time, raising RPM at every speed by 14% (bigger difference in daily driving than it sounds) and dropping your top speed in 5th to below 155, and in 4th to around 120 +/- depending on the model of C5 you have. In this case 6th gear might be the higher speed gear now - its a difficult calculation to do but I'd expect the car would pull about 160 or more in 6th with a 3.90. (A quick my back of the envelop estimate comes up with 163).
A real consideration if quarter mile performance is your thing is this: a heavily modded 'vette has the potential to do 125-135+ in the quarter mile, meaning that with a 3.73 or 3.90, it will want to exceed the top speed the car will pull in 4th at the (stock) red line: if you have rebuilt the bottom end and valvetrain so you can rev the engine more (say to 7000) this is no problem -- you just rev higher to buy back your top speed reduction in any and all gears (top speed in 5th will be back up to about 175+, etc.), but if you have, say, a stock LS1, 2, or 6 with a Magnachrager of Procharger, then you box yourself in, you either do the final 150 feet of the quarter bouncing off your red line in 4th or you shift into 5th (which is a dog for acceleration anyway) losing the time for the shift. ((This is the reason I kept the stock ratio in my vette and why we are going back to in in the Camaro (which, even at 7200, bounced the tach in 4th at the end of the quarter now).
The 3.73 will reduce your speed at the red line in each gear by 9%, so top speed of a C5 being about 175, that will fall 9% to 160: you will just barely have what you want. It will also increase the top speed the car will pull in 6th (it will only pull about 140 stock) to about 150 (5th will still be the highest speed gear but not by much).
A more significant consideration is that your car will rev 9% higher at every speed in daily driving (you will notice the difference).
Ecklers sells a very strong 3.90 rear end which will make even more of a change, cutting .4+seconds off your quarter mile time, raising RPM at every speed by 14% (bigger difference in daily driving than it sounds) and dropping your top speed in 5th to below 155, and in 4th to around 120 +/- depending on the model of C5 you have. In this case 6th gear might be the higher speed gear now - its a difficult calculation to do but I'd expect the car would pull about 160 or more in 6th with a 3.90. (A quick my back of the envelop estimate comes up with 163).
A real consideration if quarter mile performance is your thing is this: a heavily modded 'vette has the potential to do 125-135+ in the quarter mile, meaning that with a 3.73 or 3.90, it will want to exceed the top speed the car will pull in 4th at the (stock) red line: if you have rebuilt the bottom end and valvetrain so you can rev the engine more (say to 7000) this is no problem -- you just rev higher to buy back your top speed reduction in any and all gears (top speed in 5th will be back up to about 175+, etc.), but if you have, say, a stock LS1, 2, or 6 with a Magnachrager of Procharger, then you box yourself in, you either do the final 150 feet of the quarter bouncing off your red line in 4th or you shift into 5th (which is a dog for acceleration anyway) losing the time for the shift. ((This is the reason I kept the stock ratio in my vette and why we are going back to in in the Camaro (which, even at 7200, bounced the tach in 4th at the end of the quarter now).
Thread
Thread Starter
Forum
Replies
Last Post
