Since 1979, SCS Gearbox has specialized in interchangeable gearing solutions for truck and tractor pullers.
Calculators
Utilize SCS Gearbox calculators designed to simplify gear selection, ratio calculations, and performance planning. Our intuitive tools help you find the right components for your specific needs, whether you're optimizing torque, speed, or efficiency. Use our calculators to compare gearbox options, estimate specifications, and make informed decisions for your project or vehicle setup.
Utilize our Calculators
12.66” Drop Transfer Case Calculator
Select your Lower Gear Set (Bull Gear) to compare
available quick-change gearing. The chart updates
automatically to show combined transfer case ratios.
Use the calculator to determine your transfer case
ratio, estimated vehicle speed, and overall driveline ratio.
Gear Ratio Chart
Upper Ratio
Teeth
Underdrive
Overdrive
Select a chart row to use that upper gear ratio.
Overdrive is available only where shown in the
original SCS chart.
Transfer Case, MPH & Overall Driveline Calculator
Combined Transfer Case Ratio
:1
Overall Driveline Ratio
:1
Estimated Vehicle Speed
MPH
Underdrive:
Lower Gear Ratio × Upper Gear Ratio.
Overdrive:
Lower Gear Ratio ÷ Upper Gear Ratio.
Overall Driveline Ratio:
Transmission Ratio × Transfer Case Ratio ×
Rear Axle / Differential Ratio.
MPH estimates assume direct mechanical gearing without
accounting for tire growth, drivetrain slip, or other losses.
Confirm gear compatibility with SCS Gearbox before ordering.
The SCS Straight Thru Transfer Case Calculator
You can download the Excel Spreadsheet of near the bottom of this page.
Desktop Download Recommended
10.66” & Straight Thru Transfer Case Calculator
Select your lower gear set configuration and ratios to calculate
your transfer case gearing. The chart updates automatically to
compare available quick-change combinations. Enter your engine
RPM and tire diameter to calculate estimated vehicle speed (MPH).
Gear Ratio Calculator
Combined Transfer Case Ratio
:1
Overall Drivetrain Ratio
:1
Estimated Vehicle Speed
MPH
Interactive Gear Ratio Chart
Change the lower gear ratio or configuration to update
the chart. Select a row to use its quick-change gear set.
Quick-Change Ratio
Teeth
Combined Case Ratio
Under Drive:
Lower Ratio × Quick-Change Ratio.
Overdrive:
Lower Ratio ÷ Quick-Change Ratio.
Overall Ratio:
Transfer Case Ratio × Rear End Ratio × Transmission Ratio.
Estimated MPH:
Engine RPM × Tire Diameter ÷ (Overall Drivetrain Ratio × 336).
MPH estimates do not account for tire growth, drivetrain slip,
or other mechanical losses. Verify gear compatibility with
SCS Gearbox before ordering.
The SCS UnderDrive Calculator
You can download the Excel Spreadsheet of near the bottom of this page.
Desktop Download Recommended
Twin & Single Counter Shaft Gear Calculator
Calculate overall drivetrain gear ratios for SCS Gearbox
20, 30, and 40 Series and Twin Countershaft Transmissions.
Enter your planetary and rear-end ratios, then select
your headset and quick-change gear sets to determine
your overall two-wheel-drive gear ratio.
Calculated Overall Gear Ratio
:1
Headset Effective Ratio:
:1
Quick Change Effective Ratio:
:1
2-Wheel Drive Formula:
Planetary Ratio × Rear-End Ratio × Effective Headset Ratio
× Effective Quick-Change Ratio = Overall Gear Ratio.
For overdrive gearing, the selected ratio is applied
as its reciprocal. Gear set tooth counts and ID numbers
are based on the supplied SCS Gearbox quick-change spur
gear charts. Some gear models may have limited availability.
Verify gear compatibility with SCS Gearbox before ordering.
Straight Thru Transfer Case
Small adjustments can go a long way, make sure you have your Straight Thru Transfer Case optimized perfectly for what you need to get out of your machine!
We have a page dedicated solely to all of our Monster Truck Case Prouduct Lineup! Not sure if you see what you need? Be sure to contactour staff here at SCS Gearbox today!
