2004 GMC T6500

The 2004 GMC T6500 is a medium-duty truck designed for commercial use. While it was built to be a workhorse, owners have reported some common issues over the years. Engine options for this model year include the Duramax 6.6L Diesel and the 8.1L Vortec gas engine. Transmission options include Allison automatic transmissions. Owners generally appreciate the T6500 for its robust build and capability, but common complaints include issues related to aging components and the cost of maintenance and repairs.

Engine

Duramax 6.6L Diesel (LB7)

• Fuel Injector Failure
  • Description/Symptoms: The LB7 Duramax engine is notorious for fuel injector failures. Symptoms include rough idling, white smoke, poor fuel economy, and potential engine knocking.
  • Solution: Replacing the faulty fuel injectors is the only permanent solution.
  • Estimated Cost to Fix: $2,000 - $4,000+
  • Recalls: None Found
• Glow Plug Issues
  • Description/Symptoms: Difficult starting in cold weather, excessive white smoke on startup, and a check engine light indicating glow plug circuit malfunctions.
  • Solution: Replacing faulty glow plugs and the glow plug control module.
  • Estimated Cost to Fix: $200 - $500
  • Recalls: None Found

Vortec 8.1L Gas

• Exhaust Manifold Bolts
  • Description/Symptoms: Broken exhaust manifold bolts, causing exhaust leaks, ticking noises, and reduced fuel efficiency.
  • Solution: Replacing the broken bolts, and potentially the exhaust manifold if it is warped or damaged.
  • Estimated Cost to Fix: $300 - $800
  • Recalls: None Found
• Oil Leaks
  • Description/Symptoms: Oil leaks from various engine seals and gaskets, including the valve cover gaskets, oil pan gasket, and rear main seal.
  • Solution: Replacing the leaking seals and gaskets.
  • Estimated Cost to Fix: $100 - $1000+ depending on the leak’s location.
  • Recalls: None Found

Transmission

Allison Automatic Transmissions

• Shift Flare
  • Description/Symptoms: Delayed or erratic shifting, particularly between gears. This can be more pronounced under heavy load.
  • Solution: Can be caused by worn clutches, faulty solenoids, or valve body issues. Diagnosis and repair by a qualified transmission shop is essential. In some cases, a full transmission rebuild is necessary.
  • Estimated Cost to Fix: $500 - $4,000+ depending on the severity.
  • Recalls: None Found
• Torque Converter Issues
  • Description/Symptoms: Shuddering or vibrations at specific speeds, particularly under light acceleration. Can also cause overheating.
  • Solution: Replacement of the torque converter.
  • Estimated Cost to Fix: $800 - $2,000+
  • Recalls: None Found

Suspension

• Leaf Spring Sagging/Breaking
  • Description/Symptoms: Reduced ride height, poor handling, and potential cracking or breaking of the leaf springs, especially under heavy loads.
  • Solution: Replacing the worn or damaged leaf springs. Upgrading to heavier-duty springs may be beneficial for trucks frequently used for heavy hauling.
  • Estimated Cost to Fix: $500 - $1500+ per axle
  • Recalls: None Found
• Worn Ball Joints and Tie Rod Ends
  • Description/Symptoms: Loose steering, clunking noises from the front end, and uneven tire wear.
  • Solution: Replacing the worn ball joints and tie rod ends, followed by a wheel alignment.
  • Estimated Cost to Fix: $300 - $800+
  • Recalls: None Found

Electrical

• Wiring Harness Issues
  • Description/Symptoms: Corrosion and damage to wiring harnesses due to exposure to the elements and harsh operating conditions. This can lead to various electrical problems, including sensor failures, lighting issues, and starting problems.
  • Solution: Repairing or replacing damaged sections of the wiring harness. Using dielectric grease on electrical connections can help prevent future corrosion.
  • Estimated Cost to Fix: $100 - $1000+ depending on the extent of the damage.
  • Recalls: None Found
• Alternator Failure
  • Description/Symptoms: Battery not charging, dimming headlights, and eventual engine stalling.
  • Solution: Replacing the faulty alternator.
  • Estimated Cost to Fix: $200 - $600
  • Recalls: None Found

Exterior

• Rust
  • Description/Symptoms: Rust formation, particularly in areas prone to salt exposure or moisture accumulation. Common areas include the cab corners, rocker panels, and frame.
  • Solution: Repairing or replacing rusted panels, and applying rust inhibitors.
  • Estimated Cost to Fix: $200 - $2000+ depending on severity
  • Recalls: None Found

Interior

• HVAC Blower Motor Failure
  • Description/Symptoms: Blower motor stops working or only works on certain speeds.
  • Solution: Replacing the blower motor resistor or the blower motor itself.
  • Estimated Cost to Fix: $100 - $400
  • Recalls: None Found

Summary

The 2004 GMC T6500, while a capable work truck, does have some common issues owners should be aware of. The Duramax diesel engines are prone to fuel injector failures. Rust, and electrical issues are also common due to the truck’s age and exposure to harsh conditions. Repair costs can range from a few hundred dollars for minor fixes to several thousand for major engine or transmission repairs. Potential buyers should carefully inspect the truck for signs of these issues and budget accordingly for potential repairs.