Gear Ratio Calculator

© 2008-2013 All Rights Reserved

This form allows you to calculate final drive ratios as well as see a comparison of speeds and RPMs within operating ranges of the vehicle. This calculator is useful for planning your rig, allowing you to see what kind of performance to expect from different combinations.

Disclaimer: This form is only to be used for estimation purposes. Exact results of combining equipment may vary from the estimates provided in this form. The data provided here is done so as-is with no warranty expressed or implied.

Note: This calculator is continually being updated. The lists of available equipment will probably never be complete. If you find that the parts you would like to use are not yet listed, please send the information to me at grimmjeeper@gmail.com and I will do my best to include it as quickly as possible. You can also follow this site on Facebook.

Detailed Instructions Here

Choose between SAE (feet/miles) and Metric (meters/kilometers)

Save the entries in the form for when you come back later Or clear them entirely
Note that this will store the data locally on your computer. Nothing you do is tracked on the grimmjeeper server.

Step 1: Select transmission from the drop down list or, if it's not in the list and you know the gear ratios of your transmission, enter them below.

Number of forward gears
1st Gear

x

2nd Gear

x

3rd Gear

x

4th Gear

x

5th Gear

x

6th Gear

x

7th Gear

x

8th Gear

x

9th Gear

x

10th Gear

x

Reverse

x

Manual or Auto with lockup torque converter
Automatic without lockup toque converter

Step 2: Select transfer case from the drop down list or, if it's not in the list and you know the gear ratios of your transfer case, enter them below.

High Range

x

Low Range

x

STaK Range

x

Step 3: Select underdrive.

High Range

x

Low Range

x

Step 4: Enter axle gear ratio.

Step 5: Select tire size.

Inch
mm
P-Metric /R

The following chart lists the final drive ratio of all combined gears (transmission, transfer case, underdrive, axle) in all possible combinations

Final Drive Ratio
Gear Underdrive Hi Underdrive Lo
Tcase Hi Tcase Lo STaK Tcase Hi Tcase Lo STaK
1 - - - - - -
2 - - - - - -
3 - - - - - -
4 - - - - - -
5 - - - - - -
6 - - - - - -
7 - - - - - -
8 - - - - - -
9 - - - - - -
10 - - - - - -
R - - - - - -

The following chart lists the crawl speed you will be going while the engine is at a given RPM. Crawl speed is calculated based on the lowest low range (transfer case and underdrive in low range) available in your rig.

Crawl Speed at given RPM in feet per minute
Gear RPM RPM RPM
FPM MPH FPM MPH FPM MPH
1 - - - - - -
2 - - - - - -
3 - - - - - -
4 - - - - - -
5 - - - - - -
6 - - - - - -
7 - - - - - -
8 - - - - - -
9 - - - - - -
10 - - - - - -
R - - - - - -

The following chart lists the road speed you will be going while the engine is at a given RPM. Road speed is calculated based on the transfer case and underdrive being in high range.

Road Speed at given RPM in Miles Per Hour
Gear RPM RPM RPM
1 - - -
2 - - -
3 - - -
4 - - -
5 - - -
6 - - -
7 - - -
8 - - -
9 - - -
10 - - -
R - - -

The following chart lists the RPMs your engine will be turning while driving at a given speed.

Road RPMs at given speed in miles per hour
Gear
1 - - -
2 - - -
3 - - -
4 - - -
5 - - -
6 - - -
7 - - -
8 - - -
9 - - -
10 - - -
R - - -

Step 1: Select transmission from the drop down list or, if it's not in the list and you know the gear ratios of your transmission, enter them below.

Number of forward gears
1st Gear

x

2nd Gear

x

3rd Gear

x

4th Gear

x

5th Gear

x

6th Gear

x

7th Gear

x

8th Gear

x

9th Gear

x

10th Gear

x

Reverse

x

Manual or Auto with lockup torque converter
Automatic without lockup toque converter

Step 2: Select transfer case from the drop down list or, if it's not in the list and you know the gear ratios of your transfer case, enter them below.

High Range

x

Low Range

x

STaK Range

x

Step 3: Select underdrive.

High Range

x

Low Range

x

Step 4: Enter axle gear ratio.

Step 5: Select tire size.

Inch
mm
P-Metric /R

The following chart lists the final drive ratio of all combined gears (transmission, transfer case, underdrive, axle) in all possible combinations

Final Drive Ratio
Gear Underdrive Hi Underdrive Lo
Tcase Hi Tcase Lo STaK Tcase Hi Tcase Lo STaK
1 - - - - - -
2 - - - - - -
3 - - - - - -
4 - - - - - -
5 - - - - - -
6 - - - - - -
7 - - - - - -
8 - - - - - -
9 - - - - - -
10 - - - - - -
R - - - - - -

The following chart lists the crawl speed you will be going while the engine is at a given RPM. Crawl speed is calculated based on the lowest low range (transfer case and underdrive in low range) available in your rig.

Crawl Speed at given RPM in Feet Per Minute
Gear RPM RPM RPM
FPM MPH FPM MPH FPM MPH
1 - - - - - -
2 - - - - - -
3 - - - - - -
4 - - - - - -
5 - - - - - -
6 - - - - - -
7 - - - - - -
8 - - - - - -
9 - - - - - -
10 - - - - - -
R - - - - - -

The following chart lists the road speed you will be going while the engine is at a given RPM. Road speed is calculated based on the transfer case and underdrive being in high range.

Road Speed at given RPM in Miles Per Hour
Gear RPM RPM RPM
1 - - -
2 - - -
3 - - -
4 - - -
5 - - -
6 - - -
7 - - -
8 - - -
9 - - -
10 - - -
R - - -

The following chart lists the RPMs your engine will be turning while driving at a given speed.

Road RPMs at given in Miles Per Hour
Gear
1 - - -
2 - - -
3 - - -
4 - - -
5 - - -
6 - - -
7 - - -
8 - - -
9 - - -
10 - - -
R - - -