overdrive button
The overdrive button shuts off your overdrive. When you hit the button, "Overdrive Off" will light up on your dash. It will automatically reset to overdrive on when you restart your engine. So why would you want to do this? Overdrive gives you the best possible gas mileage, but will in effect lower the amount of available torque. So, driving in very hilly conditions, such as mountains, or possibly when towing a very heavy load, you might benefit from turning overdrive off. This will keep your tranny from "gear hunting" and keep your engine revs up. Your owners manual will also discuss this, but not in much detail. Overdrive has nothing to do with 2 or 4 wheel drive, both can have it.