What is the toyota tundra overdrive button?

The Toyota Tundra overdrive button functions as a way to lock Your truck out of overdrive, or the highest gear. This is particularly useful if You're looking for a few quick horsepower in an emergency situation, or if You're just looking to pass a car on the highway; it enables lightning fast acceleration, which is something You wouldn't typically have in Your truck's top gear. Pressing the button can also be helpful if You're trying to merge onto the highway, exiting the highway, or going up a long, shallow grade at high speeds. The possibilities are virtually endless; use it any time You want a speed boost for quick handling. It's recommended that You don't use it in severe winter weather though, as the additional torque can reduce Your traction on the roadways.