jorobins538
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Chicago
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Message Posted: May 4, 2012 9:24:04 AM
http://en.wikipedia.org/wiki/Overdrive_%28mechanics%29
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MertieMan
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Lexington
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Message Posted: May 4, 2012 8:51:07 AM
Overdrive kicks in automatically on most vehicles and there is a switch or lever to turn it off. It is basically another higher gear to make your vehicle pull less rpms at higher speeds, thereby giving you more milage for your gasoline. Overdrive does not work at slower speeds.
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probedude2
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Akron
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Message Posted: May 4, 2012 12:58:01 AM
Uhh...
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Need_Batteries
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Vancouver
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Message Posted: May 4, 2012 12:38:38 AM
Pretty much well what they said before me...
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WEPSMAN
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South Dakota
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Message Posted: May 3, 2012 8:06:29 PM
It is good to shut off OD when you are in hills or towing when the transmission will shift alot. Going down the highway, OD will improve your mileage due to lowering RPM's.
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Wildhare57
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York
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Message Posted: May 3, 2012 3:45:05 PM
Thank you everyone - I will be reading my manual tonight to make sure I am using it correctly!
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14smoke
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Birmingham
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Message Posted: May 3, 2012 1:09:48 PM
Simple, when the OD is engaged, it allows the transmission to go into another, taller, gear, lowering the rpms your engine is turning at speed. Normal highway driving you will note this.
When you turn the OD button to the "off" position, or press it where it says it is off, you will not go into said taller gear, and at speed, the engine will be turning higher rpm's. The higher the rpms, the more gas you use as a general rule, so, long story short, yes, it can affect gas mileage.
As others have said, consult your owner's manuals about proper times to use and not use the button.
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Titanic1985
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South Carolina
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Message Posted: May 3, 2012 10:56:14 AM
Hello GBHUGVA. You said, "Keep it on except for towing". I know what you meant to say, but didn't you say it backwards? It should read keep the overdrive lockout OFF except for towing. In other words drive the vehicle normally except when towing or carring a heavy load. You would want the vehicle to use overdrive for increased gas mileage and decreased engine wear (e.g. lower RPMs).
I've done the same thing on some of my posts, thinking one thing, and wording it to say the opposite. I just didn't want to confuse Wildhare57. Your advise to read the owner's manual would have clarified that point. Best wishes :-).
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Titanic1985
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South Carolina
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Message Posted: May 3, 2012 10:44:31 AM
Hello Wildhare57. The over-drive lockout is used when towing or hauling heavy loads. It prevents possible damage to the transmission (e.g. constant downshifting/upshifting) when on hilly and level terrain respectively. I had this feature on my 1994 Dodge B250 Ram Van (3/4 ton) which was sold as "trailer ready". I pulled a 25' RV. Yes, leaving the vehicle with the lockout engaged and no load will decrease your miles per gallon and increase your RPMs. There isn't any real reason to do so.
In my case, Dodge did not fully implement the "trailer ready" package as it did not inlude a heavy duty flasher, or the necessary wiring for a trailer (had to purchase them separately). More importantly, they did not include a 410 rear end for towing, but rather a 373. This mandated the use of the over-drive lockout when towing up hills. My assumption regarding the gearing is that the vehicle would normally be used for normal driving and a 410 rear end would provide much poorer gas mileage. By the way, the engine was a 318 cubic inch V-8.
Good advice from GBHugvA and bluenvoy, consult your Owner's Manual for more specific details directly related to each vehicle. You are smart for asking as Vin63 suggested, it will "protect the transmission". Take care :-).
[Edited by: Titanic1985 at 5/3/2012 11:45:47 AM EST]
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GBHUGVA
Champion Author
Virginia Beach
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Message Posted: May 3, 2012 9:31:38 AM
Keep it on except for towing, thats what I do, but read your owners manual to be sure for your veh.
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Vin63
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San Bernardino
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Message Posted: May 3, 2012 9:30:08 AM
In uneven terrain or while pulling a trailer/hauling heavy loads, it prevents the transmission from going into over drive or hunting for a gear between OD and the next lowest gear to protect the transmission.
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bluenvoy
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Nashville
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Message Posted: May 3, 2012 8:28:58 AM
Read the owners manuals in your vehicles. They will tell you how and when to use that button.
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OceanArcher
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Mississippi
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Message Posted: May 3, 2012 8:26:15 AM
Overdive is a method of decreasing the final drive gear ratio. With overdive engaged, the engine RPM will be less, but the car speed will still remain the same. There's no "free lunch" however, cars runing in overdrive gear are more sensitive to hills like RiceBike mentioned in his note. On the relatively flat Interstate Highways, overdrive can help you get more miles per gallon, but it's little or no help in hilly country, or around town
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ricebike
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New Jersey
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Message Posted: May 3, 2012 8:14:26 AM
towing, it'll keep the auto trans from shifting back and forth from high gear
"...to turn the final gear drive off, so as to prevent the vehicle from switching gears often when pulling loads uphill or at highway speed.
When cruisin or highway driving, leave overdrive on.
Whn city/towning turn it off."
"city traffic or under 45mph - turn OD off
Highway or over 50mph - turn OD on"
there's lots of answers; click on this link to start looking into it
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