I dropped the cltuch at 5000 and bang it went. After numerous sucessful 7000 rpm launches this one killed it. I have a gxl rear with the 3.73 or whatever the auto tranny gears are the plus is it's a posi but how much slower will it make my car to go to that rear ratio?

 

noticably slower. I know that in the 5.0 community a switch from 3.somthings to 4:10s is good for a few tenths of a second.

 

anyone disagree? I know its gonna be slow i'm so sad, what about miatas? do they have 4.1 or 4.3??? I would like a 4.3. Some people also have told me that sometimes it makes a car faster with bigger gears cause you spend a longer time in seconds at your peak HP rpm range, any trueth to that?

 

Go for the 4.3's, avaliable at rx7.com

 

I have a 4.10 differential for sale with 106K on the clock. It is not a limited-slip type though. If you are interested, drop me a PM.

 

The torque sent from the engine to the driveshaft is multiplied by the gear ratio of the selected gear. The torque sent from the driveshaft to the wheels is multiplied by the diff ratio. If you make these ratios taller (numerically lower), the torque multiplication is lower, so less torque gets to the wheels. That's why you accelerate faster in lower gears, and why a taller diff ratio will make you accelerate slower.

 

but there also comes a point where even though 4.1 might make more torque then at a specified rpm then 3.73 lets say

but also you have to shift a little earlier with the 4.1 which could mean for a point in time the 3.73 might actually produce more torque then the 4.1


but 3.73 in a gxl?

aren't they 3.9?

shouldn't be THAT much of a difference

 

I could be wrong but I think all factory manual transmission cars came with a 4.10 ring and pinion. If you want more strength, get a turbo II rear end. If you want the super hot setup, get a miata torsen limited slip and have it fitted to the GTUs' 4.30 ring and pinion. Thats what I am gonna do....some day.

 

I pm'd you I live in MD and have a 4.10 rearend ready to go.

 

Man, lots of people in MD with 4.10s

 

That's because that's what most FC's have...

 

"Man, lots of people in MD with 4.10s"

Yeah ok but I have one boxes up and ready for pick up or delivery today.

 

4.10 to 3.73 is a noticable change, I know from off roading, but in your fc, I would think that it wouldn't change your acceleration too much, but you will notice it. You will notice a higher speed to rpm ratio..ie your rpms will be slightly lower.
There is a formula for figuring that :

RPM = mph x gear ratio x 336 / tire diameter

If you are wondering what gear set would be best, here is a formula to get it, just add in your prefered rpm and speed.

Gear ratio = rpm x tire diameter / mph x 336

Leslie

 

For FCs.... all had the 4.10 rear end.
Exceptions:
Automatic cars -> 3.90 rear end
GTUs cars -> 4.30 rear end.

 

Your gear selection should be based on the torque curve of your motor. Basically you want to select a diff gear that will keep you near the peak of your torque curve for the greatest amount of time. It's been a while since I've been drag racing, but another consideration is what gear are you in and at what rpm are you when you get to the lights.

Rob

 

ok well never mind if wasn't the rear it was the carier part of the axle, i saw new one for 230 no way i'm paying that for such little part anyone got one?

 

What do you mean carrier part of the axle? I have some spare CV joints w/ axles if thats what you mean. $35 if you come pick them up (Heavy! Shipping bad!)