O/D in the city

Just curious, I have never used overdrive in town, but have been wondering if it makes any difference in gas mileage to speak of? Thanks.

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Paul O.
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No, very little difference at all; overdrive will increase gas mileage, but the effects will be the greatest at highway speeds. Think lower engine rpmΎst economy. By the way, there is nothing to gain by cancelling overdrive operation in town, this is why it is enabled by default with every key cycle.

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Errmmm, some transmissions (the A4LD comes to mind) will "hunt" under certain urban driving conditions.... newer transmissions "generally" avoid this through electronic strategy.... older transmissions depending on mechanical indications are hardest hit.
Both the A4LD and the AOT could fall prey to the extra stresses, heat and wear associated with the condition. When offering advice, we should always strive to err on the side of safety.

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Jim, the overdrive on the A4LD and AOD are an integral part of the trans, and therefore shifting in or out of overdrive was no different than any other gear; automatics were designed to shift up and down. The real problem was that the calibration of the engine controls had not yet reached the level to allow high load combined with low rpm, which resulted in many driveability concerns, including shift hunting. Fortunately, that is in the distant past now. The fact is, that in city driving, the overdrive does nothing for fuel economy, and that was the question that I hoped I answered for the poster. As for whether or not you could acutally harm the transmission, that debate could rage on forever, but I have never seen any hard evidence of it, so let's not muddy the waters here, ok?

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I don't believe I was making any waters muddy.... This NG encomapsses folks from all walks of life... including thse that are driving old technology.... not because they want to but because that's what they can afford.
Additionally, I see no debate.... early overdrive transmissions had concerns with the overdrive function. Since torque is reduced through the use of overdrive, these components were often constructed of lighter material or less substantial amounts of materials. Hunting between direct and overdrive has killed many A4LDs and AOTs.
Your advice would lead those with these older units to believe that OD is OK in urban use, quite possibly causing them financial burdens they can ill afford.
Are automatics designed to shift up and down??? Of course..... Does a certain amount of wear occur with each shift? Yes.... Will a "hunting" condition increase this wear? Yes... The transmission is chock full of sacrificial parts... if there is an action that someone can take to increase the life span of these parts, it should be made known.
I have no idea where you are going with the "overdrive on the A4LD and AOD are an integral part of the trans".... Of course this function is part and parcel of the transmission assembly..... How could it be otherwise? Even though this function is "integral" to the transmission, it does not follow that the function should either be used or allowed to operate at all times... especially when we deal with older technology.
Rather than offer a blanket "fugedaboudit" statement, these people deserve to know that there have been historical concerns with OD function in urban use. They are intelligent enough to form their own opinions as to whether they want to allow OD function or not. If they decide to cancel OD, it is their choice and, as I had stated. if we are to make an "error", our error should save us money... not cost us money.
Now... getting back to your statement about the calibration of the engine controls..... On both the A4LD and the AOT the only "engine control" I can think of involved torque coverter lock. Overdrive function depended largely on either a vacuum modulator (for engine load sense) or a throttle valve cable (again for engine load sense). Where, in Gods name, does PCM calibration enter the picture?
Remember, in this venue, the past is not so distant and decent advice for one reader is terrible advice for another.
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Well, I have plenty of experience with that as I work in a suburban venue with a lot of 45 mph driving, about 1/3 mile between probable stops... since my trans shifts pretty soft into OD anyway, i make sure to not use OD. Newer cars, fine... or if you're gonna drive it till it's three years old, fine... but older cars that you're making a hobby of seeing how long you can keep em on the road? Dont use OD when you dont need it.
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When you owed a car that had a three speed tranny did you move the selector down so it would not shift back and forth at a particular speed, as well? ;)
mike hunt

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When I owned a car with a 3 speed auto, it didn't hunt between it's non-existant overdrive and direct and it didn't have lighter overdrive parts. So... what is your point? You are only proving that apples have a different taste than oranges.... not to mention a complete lack of knowledge regarding the internals of a transmission. I suggest that you step up to the plate and offer your views along with the reasons.....

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But it did hunt between second an third at a specific speed. I am merely trying to understand the reasoning behind locking out OD when the fact is whether the selector is in D or OD the tranny will not engage the OD gear until a specific speed is reached, generally around 45 MPH What is the point of moving the selector to D, at speeds below that speed, when 'city' driving is less than 45? Manufactures suggest using D when towing or on steep down grades to hold speed, or upgrades it the tranny is hunting, generally
mike hunt

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:P
Dont be a dolt, MIKE... Tbird 3.8... it shifts into OD at 43 mph.. highest practical speed about 45!!! And expect to drive at that speed about 15 seconds at most before slowing.
And Yes! When I had a Probe MT, I drove the same streets above in 4th.. wouldnt you? When I had a Big Block FOUR SPEED manual I drove city 25 -35 mph zones in 3rd... didnt you?
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Besides that info, I had an '84 CV wagon (land yacht) that in the owner's manual stated that to avoid premature failure of the transmission to not place the selector in Overdrive when driving consistently under 35mph or in the city.
As usual, the best way to learn these things is by reading the manual....
wrote:

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To the original poster, if you are still following this and I don't blame you if you aren't- the statement I made about fuel economy I still stand on- as far as the use of overdrive is concerned, please use your own judgement. My statement was unnecessary because you did not ask that question, and I regret the argument that ensued. I wish you well.

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Paul O.
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Ted wrote:

Actually I would guess the reason its back on after every key cycle is so people won't drive down the hwy in 3rd. As for mileage it would depend on your situation but it could lower your mpg if it lugs around in OD. It is a fact with any automatic (without the torque converter locked) it will get VERY hot going up a hill in overdrive, compared to 3rd(the converter is more likely to lock in 3rd too). If you don't believe me install a trans temp gauge, then shortly after you will be installing a cooler and downshifting to 3rd when going up hills :) I personally don't put it in 3rd around town but most of the surface streets around here you hit 45 or 50 easy, there are no hills, and I also drive my cars easy. If I am pulling a trailer I will always put in in 3rd unless going down a flat stretch of hwy with the converter locked. It is absolutly amazing how fast the trans fluid can get to 300 + climbing a hill in OD.
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