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 MANUALSCHEVROLET1993SUBURBAN 3/4 TON 2WD V8-454 7.4LREPAIR AND DIAGNOSISTRANSMISSION AND DRIVETRAINAUTOMATIC TRANSMISSION/TRANSAXLECONTROL MODULEDESCRIPTION AND OPERATIONOVERDRIVE RATIO
1993 Chevrolet Suburban 3/4 Ton 2WD V8-454 7.4L
Overdrive Ratio
1993 Chevrolet Suburban 3/4 Ton 2WD V8-454 7.4LSECTION Overdrive Ratio
Overdrive Ratio Error Circuit:
The overdrive ratio is determined from input speed and engine speed.
When TCC is engaged in 4th gear, if there is more than a 200 rpm difference between engine speed and input speed for at least two seconds, code 68 will set.
While code 68 is set, the following fail-safe actions will be taken:
^ Inhibit 4th Gear
^ Inhibit TCC Operation
^ Use Default Value for Pressure (force motor duty cycle)
^ Assume Drive 4 Shift Pattern
The system will recover on the next ignition cycle.
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.