Autos W/ overdrive
 

How many of you w/ autos ever drive with the OD OFF? And If so when? I'm not really sure what it's for..

My car isn't a daily driver , motors built with a rebuilt trans and 2800 stall converter ,When I'm driving locally under 45mph I turn OD off mainly because I love the sound lol when I get on a highway OD is on

Ok that's what I've heard too under like 50mph/city drive with it OFF. And over 50mph/hwy drive with it ON.. Are there any bad affects to the transmission?

What does driving with it on or off even do?

I'm not sure.. That's what i was trying to find out as well

It's basically another gear (< 1:1) at the top-end, to keep your RPMs down at highway cruising speeds.

When I turn it on it doesn't go to 5th gear I notice it stays at 4th & it hits higher rpm

I have an auto with 4:10 gears. I only use o.d. when over 50mph. Been good for over 5yrs now.

The 4r70w trans is not a 5spd auto. Its 3spd with 4th being o.d.

So it's fine to drive with it OFF in the city and ON on the hwy?

Yes.

+1 yup

Yeah, thats because it is in effect replacing 4th gear, not gaining further mechanical advantage, but rather tuning to a better gear ratio at high speed for better MPGs on the highway, less engine wear in long distance driving, etc. Some cars do label it as another gear, but its usually called overdrive in my experience.

There's really no point in turning it off, but it won't hurt anything. You just won't be using your last gear...But you won't be using it anyway, until you're crusing.