Automatic transmissions — typical maximum torque multiplication of a torque converter In a passenger-car torque converter, the peak torque multiplication ratio (stall ratio) is typically about:

Introduction / Context:
A torque converter provides hydrodynamic torque multiplication during launch until turbine speed rises and the stator freewheels. Understanding the stall ratio helps in predicting launch feel and performance.

Given Data / Assumptions:

• Light-duty automotive converter with typical stator and pump/turbine geometry.
• No exotic high-stall racing units.
• Peak multiplication occurs at near-zero turbine speed (stall).

Concept / Approach:
Most OE converters have stall ratios between about 1.8 and 2.8. Higher values would be unusual for standard road cars and bring efficiency penalties after launch.

Step-by-Step Solution:
Identify typical range for OE converters.Choose the representative mid value: about 2.5.

Verification / Alternative check:
Spec sheets for common transmissions list stall ratios around 2.0–2.5; performance variants may approach ~3.0.

Why Other Options Are Wrong:

• 10, 25, 40: far beyond hydrodynamic converter capability for automotive applications.

Common Pitfalls:
Confusing torque multiplication with gear ratio; the converter’s effect is transient and load-dependent.

Final Answer:
2.5