The dial going clockwise:
Stock - Low - Medium - High
Low: Towing heavy and low traction situations.
Medium: Moderate towing and ideal for everyday driving situations.
High: Maximum performance - ideal for empty highway cruising.
The switch must remain plugged in to stay in the desired setting. You can run the switch into the cab or leave it tied up under the hood. Leave in one setting as much as possible.
Everyone has different driving preferences, it’s suggested that you try each setting for at least a week to see what you prefer.