Digital Ratio Adapter Controller
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1991 GMC Pickup, 1991 GMC Cab & Chassis, 1991 GMC C3500 HD, 1991 Chevrolet Pickup, and 1991 Chevrolet Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Incorrect speedometer calibration will affect operation of Rear Wheel Anti-Lock Brakes (RWAL), Electronic Control Module (ECM) and Cruise Control Module (CCM).
Digital Ratio Adapter Controller (DRAC) is a solid-state device used to change AC voltage signal from the VSS to a digital signal for speedometer operation.
The DRAC is matched to the final drive ratio of each vehicle. If the final drive ratio is changed for any reason (i.e., tires or gears), the speedometer must be recalibrated to maintain accurate speedometer/odometer reading. See SPEEDOMETER CALIBRATION under ADJUSTMENTS.