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 MANUALSGMC1991FORWARD CONTROL 3.9 L, SM465/M20REPAIR AND DIAGNOSISENGINE PERFORMANCEENGINE CONTROLS - SPECIFICATIONSQUICK-SERVICEDRIVE BELT TENSION
1991 GMC Forward Control 3.9 L, SM465/M20
Drive Belt Tension
1991 GMC Forward Control 3.9 L, SM465/M20SECTION Drive Belt Tension
BELT ADJUSTMENT
| Application | (1) Tension - Lbs. (kg) | |||
|---|---|---|---|---|
| 2.5L, 2.8L & 3.1L | (1) | |||
| 4.3L, 5.0L & 5.7L | ||||
| New Belt | 135 (61.2) | |||
| Used Belt | 90 (40.8) | |||
| 6.2L Diesel | ||||
| New Belt | 146 (66.2) | |||
| Used Belt | 67 (30.4) | |||
| 7.4L | ||||
| New Belt | 129.4-140.6 (58.7-63.8) | |||
| Used Belt | 84.4-95.6 (38.3-43.4) | |||
|
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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.