This factory service and repair manual for the 2004 GMC W3500 Forward covers a cabover offered with a 6.0L V8 of 364 cubic inches — overhead-valve, naturally aspirated, gasoline — or a turbocharged 4.8L inline-four diesel of 290 cubic inches. A single build code, W3S042, is listed. Both engines share the same brakes, steering, driveline and cab, so the manual pairs a common set of chassis chapters with engine-specific procedures, specifications, torque values, wiring diagrams and diagnostics.
Engines covered
- 6.0L V8 (364 cu in) — OHV, naturally aspirated, gasoline
- 4.8L inline-four (290 cu in) — turbocharged, diesel
Trims covered
- W3S042
Known issues on the 2004 W3500 Forward. One recall is on the federal record for the 2004 W3500 Forward. It covers trucks whose fuel switching manifold solenoids were built without enough resistance to water and salt intrusion; when a solenoid fails, fuel is routed incorrectly and can overflow back out of the filler neck, and spilled diesel near an ignition source is a fire risk. One owner complaint is also recorded, without a system category attached. Fuel storage, switching and delivery are covered in full here, with component procedures, pressure specifications, wiring diagrams for the solenoid circuit and the diagnostics to isolate a bad one.
