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#1
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Overdrive Queston
Hi all:
I am new to this group and this is my first post. (I own a 2000 Ford explorer sport with the most basic no frill engine.) Here the very newbie question: What purpose does the O/D serve? Should I leave it on or off? Someone told me that leaving the O/D on was essential for highway driving but a waste of fuel for city driving. Is this true? Does anyone actually know how the O/D works? Txs. |
#2
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> wrote in message oups.com... > Hi all: > > I am new to this group and this is my first post. (I own a 2000 Ford > explorer sport with the most basic no frill engine.) > Here the very newbie question: What purpose does the O/D serve? > Should I leave it on or off? > Someone told me that leaving the O/D on was essential for highway > driving but a waste of fuel for city driving. Is this true? > Does anyone actually know how the O/D works? Txs. > For decades, all most all normal transmissions (automatic or manual) highest gears were 1 to 1. That means that the output shaft turns 1 revolution for every 1 revolution of the input shaft. Now it is uncommon to find a vehicle that does not have overdrive. Transmissions with "overdrive" have a higher (taller) gear, like .76 to 1. That means that the output shaft turns 1 revolution for every .76 revolutions of the input shaft. That gear is over driven. The engine spins fewer RPMs at the same travel speed, and torque is greatly reduced. For almost all but the most extreme driving conditions overdrive results in better fuel mileage. I assume your transmission is an automatic? Generally the only time you should have to be concerned about taking your transmission out of "overdrive" would be if you were towing or hauling at or above you vehicles GCWR Gross Combined Weight Rating. If your transmission is continually hunting for a gear, shifting in and out of overdrive, you could use that as an indicator to leave overdrive off. |
#3
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CJ,
Thanks for the quick reply! My transmission is indeed automatic. I shall leave the Overdrive on --always, as I no towing at all. I live in drive in New Orleans, and the heaviest driving I do is in the Appalachian mountain roads with a loaded car. But from what I understand, leaving overdrive on is my best bet unless I need an inordinate amount of torque. Thanks again for your answer, and feel free to let me know if I somehow misunderstood you! |
#4
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When you are driving in the mountains, it is better to switch
overdrive off when coming down a steep grade as you get little or no engine braking with it on. I also sometimes switch it off going up grades if the transmission is shifting in and out of overdrive a lot. On 10 May 2005 15:56:58 -0700, wrote: >CJ, > >Thanks for the quick reply! >My transmission is indeed automatic. I shall leave the Overdrive on >--always, as I no towing at all. I live in drive in New Orleans, and >the heaviest driving I do is in the Appalachian mountain roads with a >loaded car. But from what I understand, leaving overdrive on is my >best bet unless I need an inordinate amount of torque. >Thanks again for your answer, and feel free to let me know if I somehow >misunderstood you! |
#5
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Interesting. I was wondering about the lack of breaking even when
coming down the rae 'hills' in New Orleans.... Plus the lack of overdrive would help to 'climb' the mountains too --right? THe rest of the time, I am leaving it on. THanks to all for the info., I really apreciatte it. |
#6
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> wrote in message oups.com... > Interesting. I was wondering about the lack of breaking even when > coming down the rae 'hills' in New Orleans.... > Plus the lack of overdrive would help to 'climb' the mountains too > --right? > THe rest of the time, I am leaving it on. > > THanks to all for the info., I really apreciatte it. Well, you seem to me to be putting on your coat and hat before checking to see if it's cold outside. If you are going up and down hills then your transmission will be "hunting" for the right gear (D or OD) and that's probably not good for your transmission. Probably best to put in in D unless you are going to be on a straight stretch for a while, over, say, 45 mph. If you are driving around the city not going over 35 then you'll probably want to keep it in D. Your transmission will most likely let you know at what speed it likes to go into OD so after you get familiar with your car you'll have a good idea when to switch to OD and when to stay in D. > |
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