This factory service and repair manual for the 1999 GMC W3500 Forward addresses two engines and one build code. The gasoline option is a 5.7L V8 of 350 cubic inches, overhead-valve and naturally aspirated; the diesel is a turbocharged 4.8L inline-four displacing 290 cubic inches. Both go into the same W3S042 cabover chassis, which is why the manual splits its engine chapters but keeps brakes, steering, driveline, cab and body work in shared sections, each with its own procedures, specifications, torque values, wiring diagrams and diagnostics.
Engines covered
- 5.7L V8 (350 cu in) — OHV, naturally aspirated, gasoline
- 4.8L inline-four (290 cu in) — turbocharged, diesel
Trims covered
- W3S042
Known issues on the 1999 W3500 Forward. One owner complaint is logged with NHTSA against this model year, and it concerns the tires. On a truck that is loaded to its axle ratings most days, that points at wheel-end work more than anything else, and the manual carries the tire and wheel specifications, the wheel-nut torque values and the tightening sequence that go with it, along with the axle, hub and brake procedures behind the wheel. Suspension specifications and the diagnostics for the systems sharing that corner of the truck are included as well.
