Parts & Accessories Peace, mercy, and blessings of God be upon you. Inspection: Free ✅ Gearbox Overhaul with Warranty, Installation, and Programming ✅ Gearbox Replacement with Warranty, Installation, and Programming ✅ Warranty from one month to one year ✅ External Cooler Installation (40,000 BTU) ✅ The GMC 6-speed gearbox (known as 6L80 or 6L90) is one of General Motors' most popular automatic transmissions, widely used in Yukon, Tahoe, Sierra, and Silverado models from 2009 to 2020. This gearbox is known for its performance and fuel efficiency compared to the older 4-speed gearbox. However, it has common manufacturing defects and important points to be aware of if you own one or are considering overhauling it: Most Common Problems and Defects: Torque Converter Failure (The "Watermelon" - Torque Converter): This is the first and most common defect in this gearbox. The torque converter clutches wear out, producing metal shavings that travel with the oil into the gearbox, damaging the oil pump and the valve body. Shifting Jerk or Slipping: Especially between first and second or second and third gears, or delayed response (slipping). Internal Piston Breakage (1-2-3-4 Piston): Causes weak hydraulic pressure, loss of some gears, or the vehicle not moving. Excessive Heat Rise: The gearbox is very sensitive to heat, especially during off-roading or towing heavy loads. Tips for Maintenance and Extending its Lifespan: Regular Oil and Filter Change: The gearbox oil (original Dexron VI type) and filter should be changed every 60,000 km. Install an Additional Gearbox Cooler: One of the best solutions to protect it from high temperatures in our climate. Disable Cylinder Deactivation System (DoD/AFM): Experts recommend programming the vehicle to disable this system to reduce continuous load and vibration on the torque converter. ✅ Welcome to our branches ✅