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Car Forum / Ford / Ford Explorer / May 2005Overdrive 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. > Hi all: > [quoted text clipped - 5 lines] > 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. 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! 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. >CJ, > [quoted text clipped - 6 lines] >Thanks again for your answer, and feel free to let me know if I somehow >misunderstood you! 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. > Interesting. I was wondering about the lack of breaking even when > coming down the rae 'hills' in New Orleans.... [quoted text clipped - 3 lines] > > 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. Ulysses, how does my transmission let me know what I need to do....(I have an automatic if it matters) Well this complicates things a bit... So if I stay under 35 and just do city driving stay out of O/D So concretly O/D should really be used when I am on the interstate, I guess. I realize these must be mega-newbie questions, and I must confess that I am now more confused than ever.... > Ulysses, how does my transmission let me know what I need to do....(I > have an automatic if it matters) What I was trying to say was that if you can "feel" the transmission shifting in and out of OD then you should shift down to D. This may save some wear on your transmission and possibly extend it's life a bit. If your engine feels like it's lagging on upgrades you should shift down to D. I also generally turn of my AC going up hills and while passing. This gives you a little extra power. > Well this complicates things a bit... So if I stay under 35 and just > do city driving stay out of O/D > So concretly O/D should really be used when I am on the interstate, I > guess. That is my opinion. You can try leaving it in OD for city driving and see if it is trying to shift into OD but this probably won't happen until you get going around 45 or so. > I realize these must be mega-newbie questions, and I must confess that > I am now more confused than ever.... Sorry. All I'm trying to say is that it's probably better to use on not use OD in such a way that it will repeatedly shift in and out of OD. You can leave it in OD while going in the city etc because it won't try to shift to OD at that point. But then there is no point in putting it in OD at that speed. >> Interesting. I was wondering about the lack of breaking even when >> coming down the rae 'hills' in New Orleans.... [quoted text clipped - 15 lines] > your car you'll have a good idea when to switch to OD and when to stay in > D. Your transmission shifts into overdrive under 35 miles per hour? Maybe with no load, but not if you are accelerating. Check that and get back to us. If you are not experiencing any gear hunting (Shifting in and out of overdrive) don't worry about taking it out of overdrive. The engine braking comments may apply to you, try it and see, that is a simple downshift... Otherwise, leave it in overdrive except for the most sever conditions. "Otherwise, leave it in overdrive except for the most sever conditions. " Ok, I will, but why did another poster recommend I take it off OD if I am doing city driving under 35 mph? Is he wrong, or is this an accepted difference of opinion? I leave my O/D on just about all the time, except going up OR down steep grades. I also turn it off for quick high speed passing. We get great gas mileage, 19 city/ 24 Highway 4.0 SOHC. I have 94,000 on her now. I attribute this gas mileage to the way I maintain the vehicle and the use of Mobile one oil. In occasion I pull our POP UP when I do I seem to be turning off the O/D more often but you will know when you need that extra torque, you'll just feel it. Searcher1 > > <thebloag@yahoo.com> wrote in message > > > Your transmission shifts into overdrive under 35 miles per hour? Maybe > with no load, but not if you are accelerating. Check that and get back to > us. If I said that then I was lying (just kidding). No, it doesn't shift into OD at 35. Somewhere around 45. I'm just trying to get him to understand how to avoid gear hunting. Somewhere around 40-45 seems to be a bad spot where it keeps going in and out of OD. A 5 mph safety margin if you will. > If you are not experiencing any gear hunting (Shifting in and out of > overdrive) don't worry about taking it out of overdrive. > The engine braking comments may apply to you, try it and see, that is a > simple downshift... > > Otherwise, leave it in overdrive except for the most sever conditions. All this discussion got me curious, so I read the owner's manual for my '05. It says the same thing many of these responses say - leave it in O.D. unless you are in a situation where it is shifting in and out a lot (such as going up a mountain) or where you need engine braking (such as going down a mountain). >> > <thebloag@yahoo.com> wrote in message >> > > Your transmission shifts into overdrive under 35 miles per hour? [quoted text clipped - 14 lines] >> >> Otherwise, leave it in overdrive except for the most sever conditions. That was good idea, looking at the owner's manual. Too bad I lost mine! Does anyone know what the OM for the 2000 says? I had another question about which is the best explorer year model, and which is the worst, but I guess I'll creat another post for that one... Thanks again >>> Interesting. I was wondering about the lack of breaking even when >>> coming down the rae 'hills' in New Orleans.... [quoted text clipped - 19 lines] >with no load, but not if you are accelerating. Check that and get back to >us. No, mine doesn't, but I have a noticeable bit of engine braking when the OD is off in those situations. With it on, the car seems to free wheel when I take my foot off the gas. (Seems..... yeah I know it really DOESN'T free wheel.) >If you are not experiencing any gear hunting (Shifting in and out of >overdrive) don't worry about taking it out of overdrive. >The engine braking comments may apply to you, try it and see, that is a >simple downshift... > >Otherwise, leave it in overdrive except for the most sever conditions. Alan Moorman The only reason some people get lost in thought is because it's unfamiliar territory. Paul Fix ================================= >Interesting. I was wondering about the lack of breaking even when >coming down the rae 'hills' in New Orleans.... [quoted text clipped - 3 lines] > >THanks to all for the info., I really apreciatte it. I leave mine off in city traffic (regular streets) and turn it on when I'm on a road where I'll be traveling over, say, 45mph or so. I like the extra engine braking I get on city streets with the OD off. Alan Moorman The only reason some people get lost in thought is because it's unfamiliar territory. Paul Fix ================================= |
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