The American-made GM 6L80 transmission took the place of the 4L60-E, 4L65-E, 4L70-E, 4L80-E, and 4L85-E, but it had some big shoes to fill. GM needed an affordable yet modern automatic transmission to take the place of legends such as the TH400 and 4L60-E in its American cars. The 6L80-E was designed for powerful generation III+ V8 engines which often appeared in GM’s lineup of brands like Chevrolet, GMC, Buick, and Cadillac. The GM-approved 6L80 was for use in a vehicle weighing up to 8,600 pounds or for those with a gross weight of 14,000 pounds. It was used most commonly in vehicles like the Cadillac Escalade, Chevrolet Avalanche, Chevrolet Silverado 1500, Chevrolet Tahoe, GMC Sierra 1500, GMC Yukon, and the H2 Hummer. 

The 4L60E, the 6L80's predecessor, was a four-speed medium-duty transmission, while the 6L80 is a six-speed medium-duty transmission that was designed for higher horsepower vehicles. The 6l80e has an RPO code of "MYC" and is manufactured in Ypsilanti, Michigan. The transmission uses direct clutch-to-clutch shifting and does not have bands. It has a deep first gear for powerful starts from a standstill. It features this gear ratio specification, which makes it compatible with the racing industry and highway driving:

• First gear: 4.02
• Second gear: 2.36
• Third gear: 1.53
• Fourth gear: 1.15
• Fifth gear: .85
• Sixth gear: .67

The tall overdrive gear allows for low RPM highway cruising, which conserves fuel. The 6L80's input torque is 440lb-ft while the maximum output torque is one of the best at 664lb-ft. As with most GM transmissions, the Turbo-Hydramatic 6L80 uses Dextron VI transmission fluid and, depending on the application, uses anywhere from 10 to 12.6 quarts. You can choose to use a 258mm or 300mm torque converter with this transmission. The 6L80 is the perfect companion for GM's LS and LSX crate engines in two-wheel drive configurations. The 6L90, the big brother of the 6L80, is even better. For both of the transmissions, however, the modular design ensures common components for the four transmissions in the six-speed family. All of the versions use an input planetary gear set and two output gear sets, which makes them easy to service. One pair meshes with the ring gear and the other meshes with the sun gear.

Features found on the 6L80 include performance algorithm braking, driver shift control, and an advanced control system with a 32-bit control module inside the transmission. Since the module is inside the transmission, you don't need additional steps to install it, making it a great drop-in. The control module compensates for normal wear and tear in the clutch plates and other components so that your 6l80e performs consistently throughout the life of the transmission. 

If you are looking to mount this transmission up to a 4x4 vehicle, check and make sure you acquire the right transfer case. The most common transfer cases used with the 6L80 transmission are the Borg-Warner BW4485 and the Magna Powertrain MP1222LD. Regardless, please confirm with your VIN the right transfer case before you purchase. 

When you are looking for the reliability of a TH-400 in a six-speed transmission – and one that will handle the horsepower and torque zone you're ready to throw at it, the 6L80E fits the bill. The TH-400 transmissions could handle the high torque of a truck and were mostly found in trucks in its heyday. Now you can have a lighter transmission and one that gets better gas mileage in a format that allows great standing stop takeoffs and better fuel economy for highway driving.