This factory service and repair manual for the 1989 GMC W6500 Forward has two engines on its list, differing in both displacement and induction: a naturally aspirated 6.5L inline-six of 396 cubic inches and a turbocharged 5.8L inline-six of 353 cubic inches. The body form is the low tilt straight truck and the trim code is W6R042. The engine sections are kept apart on that account, with specifications, torque values and diagnostic paths quoted for each build rather than averaged between them.
Engines covered
- 6.5L inline-six (396 cu in) — naturally aspirated, diesel
- 5.8L inline-six (353 cu in) — turbocharged, diesel
Body styles covered
- Straight truck, low tilt
Trims covered
- W6R042
Known issues on the 1989 W6500 Forward. NHTSA holds no recalls and no owner complaints for the 1989 W6500 Forward, so the federal record is clean. The manual therefore earns its place through routine work rather than through a fix, with procedures and specifications for both the naturally aspirated 6.5L and the turbocharged 5.8L, torque values for the assemblies each drives, and wiring diagrams for the W6R042 chassis.
