Explain over-drive to me

[lofapoo]

I'm a bit confused as to how the overdrive works in my car (yes I drive an auto 240, trade me ). Say I'm driving on the freeway at 4k with over-drive on, and click it off, it will jump to 5k. Is this because it's pushing out more power at these lower RPMs and gradually rising, and with O/D off it's making less power allowing it to rev higher easier?

Let a brotha know

Better yet, help me swap out this damn slushbox

[crzycav86]

Overdrive is simply a gear ratio less than one. That means while you're driving in your first three gears, your engine rpm will always spin faster than your driveshaft, but when your car shifts to 4th(overdrive) the rpm will be lower than the speed of your driveshaft.

Overdrive is just some fancy name for the gearing. It's a gimmick they put in car ads to say that the car will get good highway gas mileage. Pretty much every new car has overdrive. It's nothing special.

Manual 240's also have overdrive. It's the 5th gear.

[hybrid_flyer]

overdrive is basically 5th gear on a manual, its not there to provide more power, more like better gas mileage at highway speeds

[GhostDriver]

Basically, OD isn't technical for hyperdrive. The engine and transmission are below 1:1

[lofapoo]

So basically, when I'm in the freeway in third going at 4k, and I flip on the O/D, it will put itself into fourth gear, thus making it go at a lower RPM?

So unless I make it to third gear, O/D would be rendered useless, correct?

Thanks for the help guys

[masticatingcow]

So basically, when I'm in the freeway in third going at 4k, and I flip on the O/D, it will put itself into fourth gear, thus making it go at a lower RPM?

Correct.

So unless I make it to third gear, O/D would be rendered useless, correct?

Only as useless as 5th gear is while driving in 3rd on a 5-speed. If you're REALLY pegging redline in 2nd gear, the transmission might just jump to overdrive if you get off the gas real quick.

[Golden]

Automatic huh? Unplug the gray JECS thingy by the air filter box and make it shift ALOT quicker under partial acceleration. My gf's 1989 SOHC goes completely bonkers on her in the rain!

[masticatingcow]

LOL, are you trying to get rid of your girlfriend?

[240Knightrider]

wrong

Overdrive is not useless unless you are in fourth gear.

in second turn it on and turn it off, watch the rpms. the rpms will stay lower with overdrive on.

over drive on: the shift points are changed. not rendered useless.

[Dattebayo]

Wow, it got technical in here for some reason.

Can we simplify this for a minute? Overdrive is for passing and hi-speed freeway travel.

To explain, it just changes the gear shift mechanism so you shift differently, thats all.

[This space contained incorrect information, and was retracted to preserve the integrity of my nutz. Thank you.]
Modified by 2BN_S13 at 1:00 PM 7/6/2005

[Luke]

No, overdrive is when the gear ratio is below 1:1 like the guy said. In a 4-gear automatic, 4th gear is overdrive. In a 5-speed manual, 5th is the overdrive gear. What it allows is a lower rpm while running at highway speeds, resulting in better fuel economy.

240sx Gear Ratios (:1) 4-speed automatic1st - 2.79:12nd - 1.55:13rd - 1.000:14th - 0.69:1 5-speed manual 3.321 1.902 1.308 1.000 5th - 0.759

[Dattebayo]

You are telling me that 4th will not get used at all unless you press the button, huh?

[Luke]

You are telling me that 4th will not get used at all unless you press the button, huh?

Yep, it'll stay in 3rd.

O/D Off - no 4thO/D On - will shift to 4th

[PantherRacer]

This explains everything...I think I actually know what o/d really iz now! lol

[slydin'240]

I unplugged that last night and took it for a ride. I does shift alot harder but in normal traffic it feels weird. Like the transmission has to enguage when you press the gas.

[Golden]

yea, it shifts hardest when it's still cold. Actually, it's alot better for the transmission to get the shift over with quickly. Less wear on the friction surfaces inside the transmission and more wear on the friction surfaces of your ***-cheeks.