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 MANUALSGMC1995FORWARD CONTROL 4.3 Z, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - 4.3LTROUBLE CODE CHARTSCODE 87, HIGH GEAR RATIO ERROR - ALL MODELSNOTES
1995 GMC Forward Control 4.3 Z, Standard
Code 87, High Gear Ratio Error - All Models: Notes
1995 GMC Forward Control 4.3 Z, StandardSECTION Notes
Control module calculates ratio based on transmission input speed and output speed sensor readings. Control module compares known ratio to calculated ratio.
- An out-of-calibration transmission range pressure switch could falsely indicate actual transmission range.
- This test verifies proper ratio.
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.