# Overdrive on or off when hauling?



## xilikeggs0

I was told to turn the overdrive off on my truck (a 1998 Dodge Ram 2500 diesel) when pulling my trailer (a late 80's steel 3 horse slant with a dressing room), but it seems to make the engine work harder when I do that. With overdrive off, I'm at 2,400 RPMS at 60 MPH, but with it on, I'm only at 1,600. What gives?


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## Luv 2 Trail

:?I KNOW WHAT YOU MEAN! I understand drive with the OD OFF when hauling - it protects your transmission - I have an older F350 Dually and a Sooner 3 horse Slant w/dressing room - my mechanic said absolutely OD OFF when hauling or I'd be putting a new transmission in my truck!


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## BackInTheSaddleAgain

I would be interested in hearing what people do, too. We've got a HUGE trip coming up =/


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## xilikeggs0

Luv 2 Trail said:


> :?I KNOW WHAT YOU MEAN! I understand drive with the OD OFF when hauling - it protects your transmission - I have an older F350 Dually and a Sooner 3 horse Slant w/dressing room - my mechanic said absolutely OD OFF when hauling or I'd be putting a new transmission in my truck!


 Any idea why though? It obviously makes the engine work harder, so it seems like you're trading replacing the transmission for replacing the engine.


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## Chavez

I have a 2001 Toyota Tundra and a 14ft stock trailer and my garage tells me to ALWAYS drive with the OD off..Once again not sure why but that what they tell me and so does my owners manual.


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## GypsyTally921

OFF OFF OFF.

"Overdrive" is just that... here's how it works: it makes the wheels turn more than one rotation for every rotation of the transmission/ engine. So basically when you're in overdrive your wheels are spinning faster than your engine, which takes stress off the engine in normal freeway driving when the accelerated mass of your car can maintain your speed and your engine doesn't need to work as hard. But if you are towing more weight, going uphill, etc., it actually makes your engine work HARDER because it has to catch up to the wheels to push that load. It's like this: imagine (and these are just arbitrary numbers) for every 1 rotation of your engine, your wheels are spinning twice. In normal freeway driving, the mass of your car at speed helps to push itself and the engine really only needs that single rotation to every double rotation of the wheels to maintain speed. But if you add weight, you are asking your vehicle to pull up to twice its mass at half engine power. This will make your vehicle sluggish and tear up your transmission, because it's trying to convert the engine's power to wheel power at a lower rate. Your engine will bog down and have to work twice as hard to maintain the same rate of speed.

When you turn overdrive off, it sounds/ looks like your engine is working "harder" but it's really just working normally. Towing is hard on your vehicle anyway, but you are NOT doing it any favors by keeping it in overdrive, you are actually damaging more than you are helping.


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## xilikeggs0

GypsyTally921 said:


> OFF OFF OFF.
> 
> "Overdrive" is just that... here's how it works: it makes the wheels turn more than one rotation for every rotation of the transmission/ engine. So basically when you're in overdrive your wheels are spinning faster than your engine, which takes stress off the engine in normal freeway driving when the accelerated mass of your car can maintain your speed and your engine doesn't need to work as hard. But if you are towing more weight, going uphill, etc., it actually makes your engine work HARDER because it has to catch up to the wheels to push that load. It's like this: imagine (and these are just arbitrary numbers) for every 1 rotation of your engine, your wheels are spinning twice. In normal freeway driving, the mass of your car at speed helps to push itself and the engine really only needs that single rotation to every double rotation of the wheels to maintain speed. But if you add weight, you are asking your vehicle to pull up to twice its mass at half engine power. This will make your vehicle sluggish and tear up your transmission, because it's trying to convert the engine's power to wheel power at a lower rate. Your engine will bog down and have to work twice as hard to maintain the same rate of speed.
> 
> When you turn overdrive off, it sounds/ looks like your engine is working "harder" but it's really just working normally. Towing is hard on your vehicle anyway, but you are NOT doing it any favors by keeping it in overdrive, you are actually damaging more than you are helping.


 Thanks for the explanation!


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## makin tracks

Not in America, but our Nissan Patrol (1992) diesel has towed our 4 horse float for about 300,000kms and I just use our overdrive like another gear. However, there is no way I would do that with a later model as the gear boxes just are not strong enough and I know of lots of people towing far less than I do, blowing their gear boxes up very quickly.


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## Tazmanian Devil

Overdrive on causes more shifting of gears. When you drive your truck normally (OD on) and accelerate or go uphill you will notice the vehicle shifting gears. When towing, the weight of the trailer will cause this to happen more often. The frequent gear shifting when pulling weight is not good for the transmission.

When I am on level ground with OD off, my truck would shift to the higher gear and show lower engine RPM. This does not happen as often as when OD is kept on. Depending on terrain, I would sometimes turn OD back on to get the lower RPMs and better gas mileage.

My current truck calls it "tow mode" instead of OD on/off. I now always use the tow mode when towing. I do this because the mode is smarter and provide other benefits. Not only does it up-shift more reliably, but it is also smart enough to DOWN-shift on downgrades, providing some needed engine braking on hills. Thus, it not only protects the tranny by eliminating unnecessary shifting, it also protect the brakes and makes the vehicle safer on downhill stretches.

The real usefulness of the OD mode will depend on the make/model/year of the vehicle and manufacturer's implementation of the feature. Unless you are really sure of the ramifications, you are better off sticking to the manufacturer's instructions.


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## GGs

The reason you turn your OD off is that the OD is the biggest cog in the gear box there for it puts more strain on it when towing and is the easiest to damage over a long period of time


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