Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1991JIMMY 5.7 K, AUTOMATIC, 4L60/MD8REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETHEORY AND OPERATIONENGINE CONTROLS - THEORY & OPERATIONCOMPUTERIZED ENGINE CONTROLS (GASOLINE)INPUT DEVICESDIGITAL RATIO ADAPTER CONTROLLER (DRAC)
1991 GMC Jimmy 5.7 K, Automatic, 4L60/MD8
Digital Ratio Adapter Controller (DRAC)
1991 GMC Jimmy 5.7 K, Automatic, 4L60/MD8SECTION Digital Ratio Adapter Controller (DRAC)
DRAC compensates for various axle and tire ratios by monitoring the Vehicle Speed Sensor (VSS) signal and modifying it before passing it on to the ECM and speedometer unit.
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.