HELP WITH OVERDRIVE TRANSMISSION, I NEED TO KNOW WHAT OVERDRIVE DOES?? Options

[BlazedInMyCeli]

i recently purchased an automatic 97 celica ST hatchback. I have been wondering if most people leave there car in or out of overdrive? Any benefits to better mpg with overdrive??? what exactly does overdrive do?

[enderswift]

im pretty sure overdrive is a run mode for the transmission where the torque converter locks with the flywheel (usually above 40 mph), thus giving you highway cruise mileage like a manual. I've never heard of it being a separate gear... Turning overdrive off allows the flywheel to spin faster than the torque converter, which multiplies torque but wastes gas.

i've been wrong before, but im confident with this assumption

[3SGTE-auto]

im pretty sure overdrive is a run mode for the transmission where the torque converter locks with the flywheel (usually above 40 mph), thus giving you highway cruise mileage like a manual. I've never heard of it being a separate gear... Turning overdrive off allows the flywheel to spin faster than the torque converter, which multiplies torque but wastes gas.

i've been wrong before, but im confident with this assumption

That would be incorrect. Try turning off the OD button, and then count the times the car shifts gears as you accelerate on the freeway. Also, look up the definition of "Overdrive". Overdrive is defined as an transmission putting out output which is faster than the input speed (RPM).

The torque converter lockup is something that should occur automatically, and in the electronically controlled transmissions, this is controlled to occur when there the engine is not under heavy load and when at crusing speed.