what exactly is Overdrive
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what exactly is Overdrive
My 05 f150 5.4 Screw automatically turns the overdrive on when i start my truck. Is it supposed to be on all the time? What exactly does it do? I noticed that it keeps my rpm's lower than when its off.
Cargo Master
Joined: Aug 2002
Posts: 2,117
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From: Over Yonder, MN
Overdrive is basically an additional gear in the transmission designed to produce a high gear ratio, as you’ve noticed your RPMs are lower because of it. It’s there to keep your engine RPMs low while cruising to save gas, something you’d want to turn off while towing or hauling heavy loads.
MMNC (SS)(Ret)
Joined: Mar 2004
Posts: 11,606
Likes: 149
From: SE Georgia
yes, your O/D is supposed to be on all the time. (if that little O/D button is on, that means the O/D is turned off. the O/D button should only light up when you turn O/D off.)
your transmission runs on a ratio system.
(these are made up #'s, but I think you'll get the point)
1st 4 to 1
2nd 3 to 1
3rd 2 to 1
4th .8 to 1
the "4" in 4 to 1 represents the # of times your engine will turn for every turn of the driveshaft. the engine will turn 4 times producing 1 turn of the driveshaft. so, in 1st gear, you have the most amount of power available to get the truck moving and the ratio gets smaller in each gear as less force is needed to maintain/gain forward momentum. by the time your in O/D, the engine is turning < 1 turn to provide that 1 turn of the driveshaft.
once your up to speed, you can lower the ratio really low...this allows the engine to run at the lowest RPM possible to maintain that speed. which equals better MPG
your transmission runs on a ratio system.
(these are made up #'s, but I think you'll get the point)
1st 4 to 1
2nd 3 to 1
3rd 2 to 1
4th .8 to 1
the "4" in 4 to 1 represents the # of times your engine will turn for every turn of the driveshaft. the engine will turn 4 times producing 1 turn of the driveshaft. so, in 1st gear, you have the most amount of power available to get the truck moving and the ratio gets smaller in each gear as less force is needed to maintain/gain forward momentum. by the time your in O/D, the engine is turning < 1 turn to provide that 1 turn of the driveshaft.
once your up to speed, you can lower the ratio really low...this allows the engine to run at the lowest RPM possible to maintain that speed. which equals better MPG
Senior User
Joined: Apr 2006
Posts: 248
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From: Escondido, Ca
When I first drove my 04 FX4, even though I knew better, it felt more it had a 4 speed with OD...there is a substantial drop in rpm when the converter locks up. A six speed would really wake up these trucks...ship them from the factory with 4:11 gears!!
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Postmaster
Joined: Nov 2004
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From: Marion, VA
Overdrive means the shaft going into the transmission from the engine is turning slower than shaft connected to the driveshaft going out.
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MMNC (SS)(Ret)
Joined: Mar 2004
Posts: 11,606
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From: SE Georgia
Originally Posted by slf06150
Overdrive button on or off does not change the shift points. If O/D is off your RPM's will be higher when cruising on the Highway/Interstate only.
if o/d is off, you are in 3rd gear. that is why your rpm's are higher. the engine is spinning faster to maintain vehicle speed. it's the same as if you put the gear selector in 2nd. you cannot use 3rd while the selector is in 2nd. or 2nd if 1st is selected. if you push the o/d button, the transmission removes 4th gear from your use.
c'mon people, there is nothing special about O/D. it's just another gear that got a special label and manufacturers started using it as a selling feature because it drastically improves your fuel economy.
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