ACCELR8

How can the effects of changing rear end gears be mathematically quantified at a given mph and/or rpm? I have a dyno graph with rwhp and rwtq and would like to use this information in conjunction with my transmission and rear end gear ratios to make an objective determination of which rear end gear I should go with.

Here is an example of where my confusion lies. Currently, with my 3.42 gears I shift out of 1st at around 45 mph. If I change to 4.10 gears I'll shift at around 37 mph. So the question is which setup will be quicker between 37 mph and 45 mph? In the first scenario the car is at a higher rpm (torque = X), in 1st gear (2.66 gear ratio), and has a 3.42 rear end gear. In the second scenario the car is at a lower rpm (torque = Y), in 2nd gear (1.78 gear ratio), and has a 4.10 rear end gear. This may be splitting hairs, but if I can quantify this, then I'll be able to quantify the effects of changing gears across the entire rpm band and, hence, be able to make an educated decision.

I hope I've explained my question clearly. If not, please ask for clarification.

Thanks,

Jim

keliente

iTrader: (22)

Does this help? www.f-body.org/gears

ACCELR8

Thanks for the quick reply.

I have used that web page to determine my mph at different rpm's and it is very helpful. However, I would like to go one step further and take into consideration my engine torque when selecting a rear end gear. For instance, a car that makes a ton of low end torque may perform better with a set of 3.42 gears than with a set of 4.10's while a car that makes a ton of high end torque may perform better with 4.10 gears rather than 3.42's. I just don't know how to mathematically consider torque when determining which gear I want to go with.

Thanks,

Jim

xpndbl3

iTrader: (23)

up to a certain trans gear, the vehicle with the biggest rear end gear will be the fastest in acceleration assuming traction is not an issue.

ACCELR8

Anyone else?

Thanks,

Jim