For sake of discussion lets use my 1995 Camaro M6 with around 400RWHP. We all know the M6 f-bodies come with 3.42 gears stock.

1.When racing in the 1/4 mile, does going with a lower ratio gear IE: 4.10's ALWAYS net faster ET's and higher MPH over something higher ratio IE: 3.42's assuming there is zero wheel spin?

2. When does running too low a gear IE: 4.10's or 4.56's become counter productive, obviously excessive wheel spin and MPG but what else?

3. Do 4.10's put more torque or HP to the ground than 3.42's?

4. What effects do gear changes have on chassis dyno results?

 

1.If you use the 4.10's and have no traction problems,
you will be faster, with-out a doubt

You will have a better e.t but not always a faster mph
MPH = hp
et= traction

2.I went from 2.73's to 3.42's and lost about 1.5mpg.
It depends on how you use the car: lots of highway miles?

3. 4.10's will put more torque to the ground, then traction may suffer.

4. Chassis dyno will read same hp, but higher torque b/c steeper gears mutiply torque.

 

you really want to ride the end of fourth gear out as you cross the trap. So with a 400rwhp m6 car lets just say its going to shift at 6800 6900. So you want a 4.10 or maybe 4.30 gear if your going to stay na. You dont want to hit fifth gear and you dont want to sell yourself short either so finding the right cam, gear, tire height, trans all need to be matched to one another. The tire height would come in last after everything else is done.

 

Thanks guys.
I am currently replacing my 10 bolt w/ 4.10's with a 9" w/ 3.90's. With the 10 bolt on street tires I could only dump the clutch at 3.5K RPM, anything more would just smoke the tires. Also in the colder months the 4.10's would break the tires loose very easily. It also appeared that going through the traps I was coming close to my 6.3K RPM redline.

I understand the the more massive 9" and the reduced efficiency will play a small part in reducing RWHP. Based on all this I chose to go 3.90's, I hope it was a good decision and the impact on performance is minimal.

 

For maximum 1/4 mile performance, typically you want your car geared so it will be at the shift-point RPM (max torque curve) at the 1/4 mile stripe.

For example; if your shift-point RPM is 6700 and with 3.23s (high gears) you're crossing the stripe at 5400, you're leaving a lot of ET on the table.

The other problem with too low of gears (extreme 4.XXs) is running out-of-gear in the 1/4. Where you're already red-lined on the tach, but haven't made it to the stripe.

Warren Johnson always says, "turn it 5% over at the stripe."

WD

 

I went with 4.10s on my m6 last summer- and went from 12.7's to 12.3's but still had 113.7mph trap speeds...
but now im crossing the line at 6000 instead of 5600....