Torque Converter Slip Calculator

Use this calculator to determine the percentage of slip in your vehicle's torque converter. Understanding slip can help diagnose transmission issues or optimize performance.

Engine RPM: RPM

Transmission Gear Ratio:

Rear Axle Ratio:

Tire Diameter: inches

Vehicle Speed: MPH

Understanding Torque Converter Slip

A torque converter is a fluid coupling that transfers power from your engine to your automatic transmission. Unlike a manual clutch, it never fully locks up in all conditions, leading to a certain amount of "slip." This slip is the difference between the engine's rotational speed and the transmission's input shaft speed.

Some slip is normal and necessary for smooth operation, especially at low speeds or when accelerating from a stop. It allows the engine to continue running even when the vehicle is stationary and provides torque multiplication. However, excessive slip can indicate a problem, such as a worn-out converter, low fluid pressure, or an issue with the lock-up clutch (if equipped).

Calculating torque converter slip helps you monitor your transmission's health and efficiency. High slip percentages (e.g., above 5-10% at cruising speeds when the lock-up clutch should be engaged) can lead to:

Reduced fuel economy
Increased transmission fluid temperature
Premature wear of transmission components
Loss of power to the wheels

This calculator estimates the slip percentage by comparing your actual engine RPM to the theoretical engine RPM required to achieve your vehicle's speed, given your gear ratios and tire size. A negative slip percentage might indicate an error in your input values or, in some rare cases, a very efficient lock-up clutch or measurement inaccuracies.

How to Use the Calculator

Engine RPM: Enter the current RPM reading from your tachometer.
Transmission Gear Ratio: Input the ratio for the specific gear you are currently in (e.g., 1.00 for 4th gear in many transmissions, or overdrive ratios like 0.70). Consult your vehicle's manual or transmission specifications.
Rear Axle Ratio: Enter your vehicle's rear differential gear ratio (e.g., 3.73, 4.10).
Tire Diameter: Measure or look up the overall diameter of your vehicle's tires in inches.
Vehicle Speed: Enter your current speed in Miles Per Hour (MPH).

The calculator will then provide an estimated torque converter slip percentage. Remember that this is an estimation, and actual slip can vary based on many factors, including load, throttle position, and fluid temperature.

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