1998 GMC Forward Control 7.4 BFACTORY OEM SERVICE PROCEDURE

Lubrication Specifications

LUBRICATION SPECIFICATIONS

Application Specification
Automatic Transmission Dexron-III ATF
Brake Master Cylinder Delco Supreme 11 Or DOT 3
Hydraulic Clutch System Delco Supreme 11 Or DOT 3
Cooling System (1) DEX-COOL & Water 50/50 Mix
Engine Oil
Light Duty Gasoline (GVWR 8500 Or Less) (2)
Operating Temperature
All Climate Conditions SAE 5W-50 API SH/CD
More Than 0°F (-10°C) SAE 10W-30 API SH/CD
Heavy Duty Gasoline (GVWR 8501 Or More) (2)
Operating Temperature
More Than 0°F (-10°C) SAE 10W-30 API SH Preferred
Less Than 60°F (16°C) SAE 5W-30 API SH
Diesel Engines (2)(3)
Operating Temperatures
More Than 0°F (-18°C) SAE 15W-40 CF-4/SH or CE/SH
Less Than 32°F (0°C) SAE 10W-30 CF-4/SH or CE/SH
More Than 40°F (4°C) SAE 30 CF-4/SH or CE/SH
Power Steering Power Steering Fluid (GM 1050017)
Differential (4)
Rear (Non-Locking) SAE 80W-90 API GL-5
Rear (Locking) SAE 80W-90 API GL-5
3500HD (5) SAE 80W-90 GL-5 or SAE 75W-140 Synthetic Gear Lubricant
Wheel Bearings NLGI Grade 2 Category GC-LB
Drive Shaft U-Joints NLGI Grade 2 Category GC-LB
Steering Linkage (6)(7) NLGI Grade 2 Category GC-LB
Ball Joints (6)(8)(9) NLGI Grade 2 Category GC-LB
King Pin Bushings (7)(9) NLGI Grade 2 Category GC-LB
Weatherstrip Dielectric Silicone Grease
(1) All Models use DEX-COOL engine coolant (orange colored, silicate-free).
(2) DO NOT use SAE 10W-40, 20W-50 or any other viscosity than those recommended.
(3) For Diesel Engines SAE 15W-40 is preferred for use where temperatures are above 0°F (-18°C).
(4) In Canada and cold climates use SAE 80W API GL-5.
(5) To reduce maintenance use SAE 75W-140 synthetic lubricant. NOTE: Before using SAE 75W-140 fluid the old fluid must be DRAINED & FLUSHED with clean mineral based (non-synthetic) axle lubricant. Refill with new SAE 75W-140 synthetic.
(6) Use low pressure grease gun to prevent seal damage.
(7) Fill until lubricant squeezes out from base of seals.
(8) Fill ball joint until seal starts to swell.
(9) CAUTION: DO NOT grease ball joints or king pin bushings if the component temperature is below 10°F (-12°C).
Factory Service Tools

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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.

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