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Home >> GMC >> 1991 >> C3500 HD 6.2 J, Automatic >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Instrument Panel - C/K Series Pickups >> Description & Operation >> Digital Ratio Adapter Controller

Digital Ratio Adapter Controller

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.