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Distance in 1st Gear Calculator

When choosing gear ratios for your transmission and/or rear end, it’s very important to get a good 1st gear ratio.  In fact, I believe it’s a bit more important than the final gear ratio.   

Your Starting Line Ratio (SLR) is a great place to start, but it only reflects part of the info you need to decide on gear ratios.   For example, I have a 4.33 rear gear with a 2.87 1st gear, which is a 12.4 SLR.  That will seem pretty steep to most, but my 31” tires really tame that down to a usable ratio.  So, “by how much” you might ask?   Until I was able to build this calculator, I couldn’t tell you with hard numbers.

This calculator is intended to give you a reasonable approximation of how far your car will travel until you need to shift into 2nd gear.

Yes, there are many variables that will affect this calculation, and ‘no’ this calculator doesn’t attempt to incorporate all possible factors.  For example, these calculations assume zero clutch and/or tire slippage.  And it assumes a linear rate of acceleration, which isn’t necessarily ‘real world’ in most cases.

However, this calculator should provide you with the ability to get an idea of how far you can expect to travel in 1st gear.  And give you a chance to see how various gear ratios will affect your 1st gear usage.  Just bear in mind these calculations give you the MINIMUM distance given the critieria.  You can always extend the distance by letting off the accelerator while driving.

Please feel free to give us some feedback and/or suggestions.  Email Us.

First Gear Ratio:

Rear End Gear Ratio:

*Engine Torque:

Tire Diameter (inches):

**Shift RPM:

Total Car Weight:

Approx Distance Travelled in 1st gear (in feet):

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  and more!

*Engine Torque:  approx. torque of your engine.   Accuracy is not drastically important, just get it close.  Also, try to consider what your engine is putting out for a ‘normal’ acceleration (i.e. from a stop light).   It won’t be putting out a peak torque # unless you have it floored.   If you’re driving a street car, take your best guess.  I chose to use 1/2 of my peak torque for street driving calculations.

**Shift RPM:  At what RPM do you want to shift at?  Consider a full-throttle run, and a ‘normal’ take-off from a stop, at which you would shift more like 2500 RPM.  On a street car, the latter is important to represent everyday driving.

Special thanks to the guys at the F-body Classic mailing list for providing us with the calculations!

Click to see Jack's calculator(s)

Credit given in blue neon lights, as requested.  :-)

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This website is a comprehensive collection of information regarding the installation of TREMEC transmissions into various vehicles. Material contained in here may be reproduced for PERSONAL USE ONLY. No material may be redistributed in electronic or printed form without the written permission of Brad Wedan (owner). Owner believes to the best of his knowledge this information to be correct, however no warranty is made as to its accuracy. Owner also disclaims any liability for financial loss, property damage or injury in connection with use of this information. Not affiliated with, endorsed or compensated by TTC, or any sanctioning body mentioned within. Any trademarked names are property of their respective trademark holder and are used for identification purposes only. Portions of this website may be copyrighted by other individuals or organizations.

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