What exactly does the "Overdrive-off" do in my car?

I've seen about .... 2-3 threads that had any amount of useful information.

Hi, I've never driven a car, but I see that little circle around the D in my parents car...
..

 

[SilentZero]

Lowers your gas milage when its off!

 

[JulesMaximus]

Originally posted by: Cyberian

Originally posted by: Zeero
it's too keep your RPM low to moderate. It's for gas saving purpose. do a search, i think there's a detailed explanation somewhere.

God, I love this place!!

Why do people who have absolutely no idea WTF they are talking about insist on making asses out of themselves??

Read my post.

 

[HOWITIS]

turn it off when you race. vroom vroom

 

[Zenmervolt]

Originally posted by: Aftermath
OverDrive = any gear ratio smaller than 1:1.
When your transmission shifts into overdrive the input from the engine is slower than the output of the transmission. It's great for highway speeds because it drops the RPM of the engine, and you maintain speed, but you lose power (which isn't necessary when you hit the cruise control on the highway anyway.) You're not supposed to use overdrive when towing anything though, and it's advised against using in town where the tranny will shift in/out of overdrive, so that's why there is an option to turn it off. On other (or maybe older, I haven't driven a new auto in years), on the gear shift you had O (with a D in it) for Overdrive, and just D for your standard gears (keeping the car from shifting into OD.)


I know I know, I'm a few hours late on this thread.

There is no need to shift out of overdrive in town. No automatic transmission would shift into top gear at 35 mph or less. The transmission should be left in Overdrive except when towing, when going up steep uphill grades and when going down steep downhill grades.

Also, the wheels of a car always spin more slowly than the engine. Even though Overdrive has a ratio less than 1:1 in the transmission, the differential ratio is generally in the area of 3.5:1 so the wheels are still spinning more slowly than the engine.

ZV

 

[wampa]

Originally posted by: Quixfire

Originally posted by: Crazymofo
It stops the trans from shifting to overdrive...

exactly

 

[cliftonite]

Originally posted by: wampa

Originally posted by: Quixfire

Originally posted by: Crazymofo
It stops the trans from shifting to overdrive...

exactly

 

[flot]

I know what overdrive does, but now I'm confused because a number of people have specifically said not to use it while towing.

This seems entirely wrong to me. AFAIK, depending on your car, overdrive will skip the top gear, AND/OR disable the torque converter lockup.

Also AFAIK, torque converter lockup is a very good thing if you are towing, otherwise your transmission will build up considerably more heat.

I think the actual statement should be "overdrive should not be used while towing in hilly or stop-and-go areas" ? Because I would think you'd absolutely want your overdrive on while towing on a smooth flat interstate situation?

 

[radioouman]

Originally posted by: flot
I know what overdrive does, but now I'm confused because a number of people have specifically said not to use it while towing.

This seems entirely wrong to me. AFAIK, depending on your car, overdrive will skip the top gear, AND/OR disable the torque converter lockup.

Also AFAIK, torque converter lockup is a very good thing if you are towing, otherwise your transmission will build up considerably more heat.

I think the actual statement should be "overdrive should not be used while towing in hilly or stop-and-go areas" ? Because I would think you'd absolutely want your overdrive on while towing on a smooth flat interstate situation?

True, but if the added weight from towing causes your transmission to constantly shift in and out of overdrive, then it is better just to leave it in one gear than shift back and forth. (Less wear on the torque converter.)

 

[acemcmac]

Originally posted by: m2kewl
get a manual, problem solved!

hey! someone had to say it!

hey dumbass, didn't I say in the begining that it said NOTHING ABOUT "OVERDRIVE OFF" IN THE MANUAL?

If you can't even read the first post through and through before shooting your mouth off... what the hell are you doing in forums?

 

[MercenaryForHire]

Originally posted by: acemcmac

Originally posted by: m2kewl
get a manual, problem solved!

hey! someone had to say it!

hey dumbass, didn't I say in the begining that it said NOTHING ABOUT "OVERDRIVE OFF" IN THE MANUAL?

If you can't even read the first post through and through before shooting your mouth off... what the hell are you doing in forums?

You flaming dumbass!
He meant a manual transmission car!
Cut off your hands before you post something else even stupider.

- M4H