Gear Ratio Calculator | Introdution to differentials and lockers | The basics of gears and why you would want to change them | Truck Norris | Grimm Jeeper | Information on donations | Home

Gear Ratio Calculator

© 2008-2015 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 [email protected] 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
3.06 2nd Gear
1.63 3rd Gear
1.00 4th Gear
0.70

5th Gear

6th Gear

7th Gear

8th Gear

9th Gear

10th Gear

Reverse 2.29 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
1.00 Low Range
4.70

STaK Range

Step 3: Select underdrive.

High Range
1.00 Low Range
2.28

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 12.24 57.53 - 27.91 131.16 - 2 6.52 30.64 - 14.87 69.87 - 3 4.00 18.80 - 9.12 42.86 - 4 2.80 13.16 - 6.38 30.00 - 5 - - - - - - 6 - - - - - - 7 - - - - - - 8 - - - - - - 9 - - - - - - 10 - - - - - - R 9.16 43.05 - 20.88 98.16 - 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 and miles per hour Gear RPM RPM RPM FPM MPH FPM MPH FPM MPH 1 55 0.63 222 2.52 443 5.04 2 104 1.18 416 4.73 832 9.46 3 170 1.93 678 7.71 1356 15.41 4 242 2.75 969 11.01 1938 22.02 5 - - - - - - 6 - - - - - - 7 - - - - - - 8 - - - - - - 9 - - - - - - 10 - - - - - - R 74 0.84 296 3.37 592 6.73

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 7 27 54 2 13 51 101 3 21 83 165 4 29 118 236 5 - - - 6 - - - 7 - - - 8 - - - 9 - - - 10 - - - R 9 36 72

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 1112 3890 7781 2 592 2072 4145 3 363 1271 2543 4 254 890 1780 5 - - - 6 - - - 7 - - - 8 - - - 9 - - - 10 - - - R 832 2911 5823

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

2nd Gear

3rd Gear

4th Gear

5th Gear

6th Gear

7th Gear

8th Gear

9th Gear

10th Gear

Reverse

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
1.00 Low Range
2.66

STaK Range

Step 3: Select underdrive.

High Range

Low Range

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 and miles per hour 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 - - -

Jeep® is a registered trademark of of Chrysler Group LLC.