Ok well, I was in my friends car today and noticed him using overdrive. When he turned it off the amount of rpms dropped dramatically. Hows this overdrive work? Me curious.

 

I have overdrive in my car too....turning it off allows the engine to rev higher in lower gears. For example, you can take the car out of overdrive and in third gear, you can pretty much red line the rpm's by just stomping on the gas.

stinks your gas tank dry, but more speed and power through the lower gears.

Turn the OD back on and your RPM's return to normal and your car will shift to the next gear...

That's my layman's understanding of it, I'm sure that someone else has something more technical.....