How To: Calculate RPM for your Gear Ratio
 

For those of you who WONDER what RPM's you will be at, at a certain MPH, in a curtain gear here is a great tool! this will help me in my decision on what gear I should get.
www.tchracing.com/tech/gearcalc

Good find! I have seen those things before...this one seems easy to use. We should move this to the "How To" Section.

hmmmm??
 

what trans do i pick for a 99 auto???

OK..now I am confused!
I was jotting in some numbers to determine what MPH I am going while in a curtain gear at a curtain RPM.

First I put in that I was at 5000 RPM in 3rd gear WITH the stock 3.27..and It calculated that I would be going 88MPH's.

Then I put in all the SAME numbers..only with 3.73 gears and it said I would only be going 77MPH's

Then I again put in all the same number as that But with 4.10 Gears And I was going slower at 70MPH's..

now......does that mean the stock 3.27 is the better gear???? cause I am going faster at curtain MPH's with 3.27 rather than the 3.73 and 4.10's...

WHats going on here?
SHOULDNT I BE GOING FASTER WITH THE 3.73 OR 4.10's???????? or is the forrmula all messed up????

:argue:

That's right. For 4.10's you will be going at higher rpms at the same speed that you did when you had 3.27's. Or, in other words, at the same rpms, you will be traveling slower with 4.10's than with 3.27's.

Did you ever have a ten speed? Think of the rear gear sproket as your transmission, and the front sproket as just like chaging gear ratios. You will have to pedal faster with the 4.10's. make sense?

4.10's are like a tourque multiplier. They don't make the car go faster, just accelerate faster. In theory, you actually loose top speed with them.

Moving to "How To's"

ok i see. after thinking about it, I can understand. lol

Great find!!

yeah, good find! I've now decided to go with 4.10's, I'll only be at 2330.8rpms at 70, and that's not bad at all.

YEA! Isnt this an Excellent tool???!?!?!?!

I always wondered what rpms I would be doing at certain speeds! :headbang:

I`ve using this for a year now and it helped me to decide to go with 3.90s for a daily driver.

That’s is a great find. But I think it is a little off. It told me that with a TR 3650, 315/35/17 Tires, and stock 3.27 gears at 5500 RPM in 5th gear that I will be going 207.264 MPH :tongue9: . I don’t think that is right. What do you guys think? I think I am going to try that out, I’ll tell you how it goes (lol) :laughing7 .

if your pulling that much in 5th gear with stock gears i would love to ride in your car

The calcualtor doesn't take wind and drag into consideration wich would require almost double your stock horsepower to achieve 5500 rpms in fifth with the 3.27 gears and the late model 5-speed trans.

The calcualtor doesn't take wind and drag into consideration wich would require almost double your stock horsepower to achieve 5500 rpms in fifth with the 3.27 gears and the late model 5-speed trans.If you put the car on a hoist off the ground and pulled 5500 rpms in 5th with no drag or resistance the rear tires would be spinning over 200 mph

The higher the gear the more turns it takes to turn the wheel once
with 3.27 gear it takes 3.27 turns of the drive shaft to turn the wheel once
thats why the motor has to turn over more(RPM) with the higher gears to achieve the same speeds as the lower gears

Nice link! thanks!!

How do you like the performance change...I think I'm gonna go with 3.90's, I do about 75 miles a day on the freeway.

i like them just thought it would be more of a through you back in your seat install. i would go with 4.10s. if you have a 5 speed definitly 4.10s.