2004 GMC W4500 Forward

The 2004 GMC W4500 Forward is a cab-over medium-duty truck popular for its maneuverability and payload capacity. The most common engine option for this model year is the Isuzu 4.8L 4HE1-TC turbocharged diesel engine, producing around 175 horsepower and 347 lb-ft of torque. Other engine options include the Isuzu 4.8L 4HE1 and the 5.7L Vortec gas engine. Transmission options were typically the Aisin A465 4-speed automatic, and the Isuzu MZZ6 5-speed manual. Owners often appreciate the truck’s tight turning radius and reliability, but some dislike the cab’s spartan interior and the limited availability of certain replacement parts.

Engine

Isuzu 4.8L 4HE1-TC (Turbo Diesel)

• Turbocharger Failure
  • Description/Symptoms: Reduced engine power, excessive black smoke, whistling noise from the turbo, and potentially an engine warning light.
  • Solution: Replacement of the turbocharger.
  • Estimated Cost to Fix: $1,500 - $3,000+
  • Recalls: None Found
• Fuel Injector Issues
  • Description/Symptoms: Rough idling, misfires, poor fuel economy, and black smoke. Can lead to engine damage if left unresolved.
  • Solution: Fuel injector cleaning or replacement.
  • Estimated Cost to Fix: $500 - $1,500+
  • Recalls: None Found
• EGR Valve Problems
  • Description/Symptoms: Rough idling, stalling, poor acceleration, and a check engine light. The EGR valve can become clogged with carbon deposits.
  • Solution: Cleaning or replacement of the EGR valve.
  • Estimated Cost to Fix: $200 - $500+
  • Recalls: None Found

Isuzu 4.8L 4HE1 (Non-Turbo Diesel)

• Fuel Injector Issues
  • Description/Symptoms: Rough idling, misfires, poor fuel economy, and black smoke. Can lead to engine damage if left unresolved.
  • Solution: Fuel injector cleaning or replacement.
  • Estimated Cost to Fix: $500 - $1,500+
  • Recalls: None Found
• EGR Valve Problems
  • Description/Symptoms: Rough idling, stalling, poor acceleration, and a check engine light. The EGR valve can become clogged with carbon deposits.
  • Solution: Cleaning or replacement of the EGR valve.
  • Estimated Cost to Fix: $200 - $500+
  • Recalls: None Found

5.7L Vortec (Gas Engine)

• Intake Manifold Gasket Leak
  • Description/Symptoms: Coolant leak, rough idling, misfires, and overheating.
  • Solution: Replacement of the intake manifold gasket.
  • Estimated Cost to Fix: $300 - $700+
  • Recalls: None Found
• Fuel Injector Issues
  • Description/Symptoms: Rough idling, misfires, poor fuel economy.
  • Solution: Fuel injector cleaning or replacement.
  • Estimated Cost to Fix: $400 - $1,200+
  • Recalls: None Found

Transmission

Aisin A465 (4-speed Automatic)

• Shift Delays/Harsh Shifting
  • Description/Symptoms: Noticeable delay when shifting gears, harsh or jerky shifts, and potential slipping between gears.
  • Solution: Fluid flush and filter change, valve body repair/replacement, or transmission rebuild/replacement.
  • Estimated Cost to Fix: $200 - $3,000+ (depending on the severity)
  • Recalls: None Found

Isuzu MZZ6 (5-speed Manual)

• Clutch Failure
  • Description/Symptoms: Slipping clutch, difficulty shifting, and clutch pedal pulsation.
  • Solution: Clutch replacement.
  • Estimated Cost to Fix: $800 - $1,500+
  • Recalls: None Found

Suspension

• Leaf Spring Sagging/Cracking
  • Description/Symptoms: Vehicle sagging, uneven ride height, and reduced load capacity. Cracks in the leaf springs can be visible.
  • Solution: Leaf spring replacement.
  • Estimated Cost to Fix: $500 - $1,200+ per axle
  • Recalls: None Found
• Worn Shocks/Struts
  • Description/Symptoms: Bouncy ride, poor handling, and excessive body roll.
  • Solution: Shock/strut replacement.
  • Estimated Cost to Fix: $200 - $600+ per axle
  • Recalls: None Found

Electrical

• Wiring Harness Issues
  • Description/Symptoms: Intermittent electrical problems, such as lights flickering, gauges not working, and starting problems. Corrosion and damaged wiring are common causes.
  • Solution: Repair or replacement of the affected wiring harness sections.
  • Estimated Cost to Fix: $200 - $1,000+ (depending on the extent of the damage)
  • Recalls: None Found
• Alternator Failure
  • Description/Symptoms: Dimming headlights, battery light on the dashboard, and eventual loss of power.
  • Solution: Alternator replacement.
  • Estimated Cost to Fix: $300 - $700+
  • Recalls: None Found

Exterior

• Rust (Cab and Frame)
  • Description/Symptoms: Visible rust on the cab, especially around the windshield and door seams. Frame rust can compromise the vehicle’s structural integrity.
  • Solution: Rust repair or panel replacement (for the cab), frame repair or reinforcement (for the frame).
  • Estimated Cost to Fix: $500 - $5,000+ (depending on the severity)
  • Recalls: None Found

Interior

• HVAC Blower Motor Failure
  • Description/Symptoms: No air blowing from the vents, or intermittent operation of the blower motor.
  • Solution: Blower motor replacement.
  • Estimated Cost to Fix: $150 - $400+
  • Recalls: None Found
• Seat Upholstery Tears
  • Description/Symptoms: Tears in the seat fabric.
  • Solution: Seat upholstery replacement.
  • Estimated Cost to Fix: $200 - $600+
  • Recalls: None Found

Summary

The 2004 GMC W4500 Forward, particularly with the Isuzu diesel engine, can be a reliable workhorse. However, prospective buyers should be aware of potential issues such as turbocharger failures, fuel injector problems, and transmission issues in the automatic versions. Rust is a significant concern, especially in regions with harsh winters. Repair costs can vary widely depending on the severity of the problem, but some repairs, like turbocharger or transmission replacement, can be relatively expensive. Thorough inspection and maintenance are crucial for minimizing downtime and ensuring the longevity of this vehicle.