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SLTDakota
Dodge Dakota
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12/28/2004
00:42:10
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 Subject: OverDrive ON/OFF?
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I have a 3.9 dakota I was wondering should overdrive be on or off.? Will off save gas or hurt my motor. I heard only when towing you should turn it off. Does it matter if its on or off?
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03Kota
Dodge Dakota
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12/28/2004
03:04:52
|  RE: OverDrive ON/OFF?
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i think it would be best to leave it on for everday driving because it saves gas. you can turn it off and it won't really hurt anything, you'll just be cruising in 3rd at about 2200 rpm's compared to 4th gear and 1600 rpms. i forgot to turn mine back on once and used almost 1/4 tank of gas in a 30 mile trip, although the way i drive could've had something to do with it too. but it doesn't hurt the engine, just sacrifices a little gas mileage. i'm basing this info on my automatic with 3.55 gears.
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RadioMan
Dodge Dakota
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12/28/2004
06:53:48
| RE: OverDrive ON/OFF?
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I never let mine go into OD while town driving so
the OD switch is pressed (off) as soon as I start
her up in the mornings.
It's also best to leave it off while towing.
Trips that keep you from starting and stopping all
the time is where OD is used best but again not
while towing.
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Dan M
Dodge Dakota
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12/28/2004
08:55:25
| RE: OverDrive ON/OFF?
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In addition to the above, I have O/D off while driving in mountains and very hilly areas.
- Dan M
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Scott
Dodge Dakota
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12/28/2004
13:49:09
| RE: OverDrive ON/OFF?
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people act like OD is some magical thing. It is simply a very low gear ratio. The only time OD should be turned off is when towing heavy loads and the torque converter isnt locking up. If the converter isnt locking then it will quickly heat up the fluid and could damage the tranny in a very short period of time. The other time would be when in a hilly area when the tranny keeps hunting between 3 and 4th, other then a little wear and tear there isnt much damage caused here, it is just annoying, so kick OD off and stay in 3rd till on more flat terrain. The engine and tranny communicate, many variables have to be met before the tranny will settle into OD. There is no need to turn it off in the city or during any anormal day to day driving.
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Jose
Dodge Dakota
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12/28/2004
15:46:00
| RE: OverDrive ON/OFF?
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Scott has a recto-cranial inversion on this one.
Most of your post is factual, but where did the "very low gear ratio" come from?
OD off just keeps the transmission from shifting to its highest gear. Torque converter lockup still happens in third.
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scott
Dodge Dakota
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12/28/2004
16:05:21
| RE: OverDrive ON/OFF?
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I agree and disagree, yes it keeps the tranny from shifting to the highest gear, but that gear is overdrive. It serves no purpose other than to save fuel economy during sustained travel above 45mph. You are right the converter can lock in 3rd as well, my bad. But it has to be above 40 or 45 i cant remeber which before the converter will actually lock.
My point was more that you dont need to touch the OD switch unless you are in hilly terrain or towing. The computers analize much more data then we do and will make the correct call based on speed, load, rpm and power curve of the engine
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FYI
Dodge Dakota
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12/28/2004
17:25:14
| RE: OverDrive ON/OFF?
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Next time you are crusing at 40 mph turn off your overdrive and guaranteed, the rpm's will increase.
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GraphiteDak
GenIII
12/28/2004
18:16:36
| RE: OverDrive ON/OFF?
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I agree with Scott for the most part on this one.
Actually with my 5-45RFE if I turn my OD off it will lock up in 3rd EARLIER.
But that is a completely electronic controlled transmission.
Many people turn their OD off when in the city but it was designed to be used automatically and is perfectly normal to leave it on. If you notie gear hunting on continuous hills or towing then you can turn it off.
As a matter of fact I leave mine ON when towing. The computer does a pretty good job managing the OD on this tranny and the one time I turned it off it hurt m MPG badly.
Oh, FYI, most 4 speed auto tranny's 3rd gear is a straight through 1:1 gear ratio. Basically NO ratio. the input shaft and output are turning the same straight through. OD is an overdrive ratio, output turning faster than the input.
On the 5-45RFE you have two OD ratios, one being a high .67:1 vs. the .75:1 the older tranny's have.
Those who have manual tranny's, the 4th gear is usually always the straight through 1:1 ratio on those.
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turbostang
Dodge Dakota
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12/28/2004
19:48:24
| RE: OverDrive ON/OFF?
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I could be wrong.. But my OD off button doesn't seem to stop my 46RE from going into 4th gear.. It just seems to stop the converter from locking up..
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Bob Lincoln
Dodge Dakota
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12/28/2004
20:17:01
| RE: OverDrive ON/OFF?
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The A500 (42RH) and A518 (46RH) are 0.69 to 1 O/D ratio, not 0.75.
It's just wasteful and revs the engine more to turn off O/D if not towing or under conditions when tranny is hunting 3-4-3. Around town, at light throttle on level ground, my tranny shifts into O/D at 35 mph and does not lug. When I need power, it downshifts for me. That's what an automatic does.
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DG
Dodge Dakota
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12/28/2004
21:10:30
| RE: OverDrive ON/OFF?
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Think outside the box for a bit.
Just because your engine is turning slightly higher revs with OD off, doesn't mean your engine is less efficient. In many cases, that extra 600-1000RPM puts your engine a little bit closer to its HP and Torque peak. And a little closer to the best flow rate for the intake manifold, etc.
There's a balance point, of course, depending on your driving style and local geography.
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GraphiteDak
GenIII
12/29/2004
00:48:40
| RE: OverDrive ON/OFF?
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.69 eh? I heard form someone here it was .75
But that makes sense I guess.
I read that the 45RFE got the mod to the .67 (then the 5-45RFE was born) when they tried to move the RPM's to stop some sort of harmonic vibrations in certain jeeps.
So we got an extra OD ratio. It rarely uses the in between one. When towing I wish there was a way to use the other one. From a print out I've seen it is .75 which is cherry when it does use it when towing slight grades.
As far as just unlocking the converter, that would not be a good thing if that was what it did. It would make lots of heat.
The OD button just drops it into 3rd like all other tranny's.
On the highway, gaurenteed you will lose MPG running with OD off. Especially at speeds around 75+
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droped 96
Dodge Dakota
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12/29/2004
01:04:40
| RE: OverDrive ON/OFF?
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well all im sayin only turn it off if u are pullin or goin up and down hills which i dont have in central texas and when u are runnin along at 70 75 push that button it will kick it up 2 about 3 grand no 2200 trust me my o/d went out and i had 2 drive it like that for a grip yes it uses more gas put u can pass people no problem but other than that it shouldnt hurt it and as far as turnin it off while in town that is crazy all youll do is waste gas and not even prove nothin other than u are not the britest bulb in the box
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RadioMan
Dodge Dakota
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12/29/2004
06:44:32
| RE: OverDrive ON/OFF?
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FYI said; "Next time you are crusing at 40 mph
turn off your overdrive and guaranteed, the rpm's
will increase."
And he is 100 and 1% correct.
A big difference in town driving.
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hey jose
Dodge Dakota
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12/29/2004
07:45:59
| RE: OverDrive ON/OFF?
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scott is spot on and YOU have not said anything that he did not only just differently. the .69 to 1 ratio of overdrive does indeed make it a "very low gear ratio" as it is turning the output shaft faster then the input shaft. next time taco, know for sure.
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Bob Lincoln
Dodge Dakota
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12/29/2004
09:09:12
| RE: OverDrive ON/OFF?
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"Think outside the box for a bit.
Just because your engine is turning slightly higher revs with OD off, doesn't mean your engine is less efficient. In many cases, that extra 600-1000RPM puts your engine a little bit closer to its HP and Torque peak. And a little closer to the best flow rate for the intake manifold, etc."
It's not SLIGHTLY higher - it's a lot higher. At 65 mph in 3rd gear, it's 2600 RPMs vs 1800 RPMs in O/D. That will cost you at least 4 mpg. Best gas mileage and highest efficiency are not always the same thing. I need best gas mileage, especially on long trips.
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My2cents
Dodge Dakota
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12/29/2004
11:27:30
| RE: OverDrive ON/OFF?
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We could argue this forever. I guess the answer to the original post is 'Maybe, depends on circumstances'. We all have opinions about the best way to do things - what works and what doesn't, and when it comes to giving advice, what works for some may not work for others.
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GraphiteDak
GenIII
12/29/2004
23:02:14
| RE: OverDrive ON/OFF?
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I was just going to say something along those lines too, this will be a forever argument.
But to clarify for those actually ASKING if it's ok to leave the OD on for everyday driving, the amswer is YES.
I've actually read where people say to always turn it off for city driving. If that was the case, it would default to "OFF" instead of "ON".
Oh and just to bring it up, I think I take mine out of OD MORE OFTEN when going downhill than uphill. I use it as an engine brake a lot. Especially when towing.
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mayo
Dodge Dakota
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12/31/2004
09:16:32
|  RE: OverDrive ON/OFF?
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stop and go traffic under 50mph, overdrive off. anything else od on. Don't forget that any gear jumping also will cost you milage as well, compared to the extra rpm's with od off at 45mph it should be about a wash in terms of mpg. Save the tranny and turn the dam thing off if driving in the city for any period of time.
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durrrr
Dodge Dakota
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12/31/2004
11:02:20
| RE: OverDrive ON/OFF?
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Mayo,
So in your own words OD should stay on for everything except stop and go driving. Even towing?! Try reading your owners manual and actually learning a little more about your tranny before you come on here talking as if you actually know anything about the subject at hand. I think just about everyone here will agree your wrong on this one.
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