Ok what is overdrive?

I have a manual myself my little 92 323 4cly. 1.6 and I was driving my girlfriends 04 hyunda accent. and it had over drive and to me what seems to happen is when I push the button the little light comes on saying its off or its on? not sure but any way when I press it i just seems to drop the trans down a gear. is that right?

is it just for pulling something or just for extra power when its needed like passing someone on the highway?

I mean I know I sound stupid but I really never though about it.

thanks for who ever wants to answer this one lol.

 

It is used for better gas mileage on a highway. I think when you turn it off your revs go up so it would seemto be lowering it a gear. When it's on your gas mileage is better. You would turn it on for a hill too so you sir are correct!

 

The term overdrive refers to a gear ratio in the transmaission. If you think of your 5 speed, the 5th gear is usually called overdrive too. The other 4 gears are then callled under drive gears...but that terminology is just not used. Overdrive means that the engine is turning slower than driveshaft speed, which helps gas mileage. The other gears the engine is turning faster than driveshaft speed, this is how you get power. If you look at charts, the overdrive gear ratio might be 0.91:1, and the first gear might be 3.5:1, for example.

 

Mazda also uses this function in the automatics. Is labeled either O/D off or HOLD on older cars. The primary function of the O/D off is to keep it out of 4th gear. If you have ever driven an auto trans up a hill with a certain incline and had the trans keep shifting down into 3 then back to 4 then back down to 3 and so on and so on, you would know how valuable that switch would be.