2020 GMC Sierra 3500 HD

The 2020 GMC Sierra 3500 HD is a heavy-duty pickup truck known for its powerful capabilities and comfortable interior. Available engines include the 6.6L L8T V8 gasoline engine producing 401 horsepower and 464 lb-ft of torque and the 6.6L L5P Duramax turbodiesel V8 which delivers 445 horsepower and 910 lb-ft of torque. The gasoline engine is paired with a 6-speed automatic transmission, while the diesel engine is paired with a 10-speed Allison automatic transmission. Owners often praise the Sierra 3500 HD for its towing capacity, refined ride quality (especially with the available adaptive ride control), and updated technology features. However, some common criticisms include the truck’s large size making it difficult to maneuver in tight spaces, and some reliability concerns with certain components.

Engine

6.6L L8T V8 Gasoline Engine

• Active Fuel Management (AFM)/Dynamic Fuel Management (DFM) Lifter Failure
  • Description/Symptoms: Engine misfires, rough running, check engine light. Often caused by collapsed lifters due to AFM/DFM system issues.
  • Solution: Replacement of failed lifters, and potentially the camshaft if damaged. AFM/DFM delete kits are sometimes installed to prevent future failures.
  • Estimated Cost to Fix: $2,500 - $5,000+
  • Recalls: None Found

6.6L L5P Duramax Turbodiesel V8

• Fuel Injector Failure
  • Description/Symptoms: Rough idle, white smoke from exhaust, reduced power, fuel in oil.
  • Solution: Replacement of the faulty fuel injector(s).
  • Estimated Cost to Fix: $800 - $1500+ (per injector)
  • Recalls: None Found
• CP4 Fuel Pump Failure
  • Description/Symptoms: Engine stalls, hard starting, metallic debris in the fuel system.
  • Solution: Replacement of the CP4 pump and potentially the entire fuel system to remove debris. Some owners choose to upgrade to a CP3 fuel pump for increased reliability.
  • Estimated Cost to Fix: $4,000 - $10,000+ (depending on the extent of damage)
  • Recalls: None Found

Transmission

6-Speed Automatic (Gasoline Engine)

• Torque Converter Shudder
  • Description/Symptoms: Shaking or shuddering felt during light acceleration, especially at lower speeds.
  • Solution: Transmission fluid flush, or replacement of the torque converter.
  • Estimated Cost to Fix: $300 - $2,000+
  • Recalls: None Found

Allison 10-Speed Automatic (Diesel Engine)

• Harsh Shifting/Slipping
  • Description/Symptoms: Abrupt or delayed shifts, transmission slipping between gears.
  • Solution: Transmission fluid flush, valve body replacement, or full transmission rebuild.
  • Estimated Cost to Fix: $300 - $7,000+ (depending on the severity)
  • Recalls: None Found

Suspension

• Front End Vibration/Steering Wheel Shimmy
  • Description/Symptoms: Vibration felt in the steering wheel, especially at highway speeds. Often linked to issues with the tires, wheel balancing, or worn suspension components.
  • Solution: Tire balancing, tire replacement, alignment, replacement of worn ball joints, tie rod ends, or other suspension components.
  • Estimated Cost to Fix: $100 - $1,000+ (depending on the cause)
  • Recalls: None Found

Electrical

• Infotainment System Freezing/Malfunctions
  • Description/Symptoms: Touchscreen freezes, unresponsive buttons, Bluetooth connectivity issues, navigation problems.
  • Solution: Software update, system reset, or replacement of the infotainment unit.
  • Estimated Cost to Fix: $0 - $1,500+ (depending on warranty coverage and the solution)
  • Recalls: None Found
• Sensor Failures (e.g., TPMS, parking sensors)
  • Description/Symptoms: Warning lights on the dashboard, inaccurate readings from sensors.
  • Solution: Replacement of the faulty sensor(s).
  • Estimated Cost to Fix: $100 - $500+ (per sensor)
  • Recalls: None Found

Exterior

• Rust on Frame/Undercarriage
  • Description/Symptoms: Visible rust formation on the frame and undercarriage components, especially in areas where road salt is used.
  • Solution: Rust removal and treatment, application of rust preventative coatings.
  • Estimated Cost to Fix: $300 - $2,000+ (depending on the severity and extent of rust)
  • Recalls: None Found

Interior

• Seat Heater Failure
  • Description/Symptoms: Seat heater does not warm up, or heats unevenly.
  • Solution: Replacement of the seat heater element or control module.
  • Estimated Cost to Fix: $200 - $800+ (per seat)
  • Recalls: None Found
• Cracked Dash Boards
  • Description/Symptoms: The Dash board exhibits cracking, which can often be attributed to prolonged sun exposure.
  • Solution: The dashboard would need to be replaced.
  • Estimated Cost to Fix: $1,000 - $2,000+
  • Recalls: None Found

Summary

The 2020 GMC Sierra 3500 HD, while powerful and capable, does have some common issues owners have reported. The most concerning are engine-related problems, particularly lifter failure in the gasoline engine and fuel system issues in the diesel. These can be costly to repair. Electrical glitches, suspension issues and transmission problems can also occur, adding to the potential ownership costs. Buyers should be aware of these potential problems and thoroughly inspect any used 2020 Sierra 3500 HD before purchasing. The severity of the issues varies, but some can lead to significant repair bills.