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I just bought a 2003 27RBS and will pick it up Monday. When towing can I use overdrive or must I disable it? I live in the upper midwest and it is fairly flat/ rolling hills. I would hate to loose the gas mileage advantage of overdrive.
 

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First off welcome to the Outbackers!

I'd double check your owners manual, my Av manual says to tow in the tow/haul mode which disables the overdrive and adjusts the shifting while towing too.
 

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Most folks would advise to turn over drive off, however, there are some out there that run with it on. It will also depend on your TV/TT combo as well. One way is to try it and if you find your TV doing a lot of searching for gears turn it off.
 

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my Av manual says to tow in the tow/haul mode which disables the overdrive and adjusts the shifting while towing too.
Steve, I don't want to start an off topic discussion, but when bringing the Outback home last week, I took note of the engine RPM's, and I based on the numbers I saw on the highway, I'd have to say that the GM tranny's still use O/D when in Tow/Haul and D on the selector, and that the Tow/Haul mode mearly tells the computer to change the shift points to a higher RPM, to get to the max HP/torque range before shifting to the next higher gear.

Mark 6:31, if your owners manual doesn't state specifically not to use O/D, then play it by ear, literally. If you find the transmission is constantly shifting between 3 an O/D, (assuming you have a 4 speed auto) then I would keep it in 3. If the tranny shifts to O/D, and stays there with the engine not lugging, you should be ok.

If there is a mechanic out there with better info, I will of course defer to his/her greater knowledge and experience.

Tim
 

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If you have a HD trans cooler you may get away with it. I have a temp gauge on my trans + a cooler and coming back from South Dakota I tried the OverDrive and I could see the trans temp go up. I talked to a repair shop and was told that most repairs are do to high heat on trans running a heavy load in overdrive. Also your gas miles will go down do to your eng. is working harder in overdrive. I tried both ways on that trip and found no great savings in overdrive.
 

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I was always told to use Overdrive when you are not loaded as an economy mode. And not to use Overdrive when you have a heavy load on the vehicle. Yes, your mileage may vary!
 

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"Come with me by yourselves to a quiet place and get some rest." (niv)

Welcome to Outbackers.com, and may I say your nickname (Mark 6:31) is most appropriate for someone planning on heading out and camping


So long as your truck is not struggling or bogging down you can tow in overdrive without any trouble. This is reccomended for flat ground, low headwind, etc... Generally in a situation where your truck is not working hard at all. Other than that 3rd gear is a better option.
 

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hatcityhosehauler said:
I'd have to say that the GM tranny's still use O/D when in Tow/Haul and D on the selector, and that the Tow/Haul mode mearly tells the computer to change the shift points to a higher RPM, to get to the max HP/torque range before shifting to the next higher gear.
Actually Tim you are correct. The tow/haul button on the GMs adjusts the shift points. In many conditions it will keep it out of overdrive, but the only sure way is to downshift out of D. Of the posts I've read and other Av owners the tow/haul mode does all that is needed unless the trans starts to hunt, in that case down shifting or slowing down is recommended. Many also find the tow/haul button should be called the Haul A$$ button instead
 

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I usually drop my 'Ho down to 3rd when towing. Especially in city or hilly driving terrain. (Tow/Haul mode)
 

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Just put it in 3rd (or Drive) not OD and forget it. I pull in 3rd only. I have put a OBD II scanner on my truck and also my brothers during towing and there is maybe .5 mpg to no difference if that by running in OD. The difference is about 1.3 to 0 gallons in 250 miles. Take it from a mechanic, it is not worth it. In OD your trans will come in and out of lockup, and down shift to Drive alot. At every shift there is a little clutch slippage, even in a new trans. This creates heat each time. If your in and out of OD alot your cooler may not keep up with the heat buildup. Heat will kill your trans fast. Put it in 3rd and have a good trip.
 

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So when people are stating they drop their transmission down to 3rd and leave it there, what kind of speed are you towing at?

One thing I noticed this weekend (towing with my Yukon XL) when I set the cruise control, my transmission seemed to shift more often, if I took the cruise off, the transmission would not shift down out of OD when climbing hills. Any thoughts on why this occured?

Thanks,
Ben
 

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My Tahoe does the same thing. I think you can control the throttle more smoothly than the cruise control does. When mine drops in speed because of a slight incline, it kicks down a gear real quick. When it's disengaged, and I'm driving myself, I can make the incline without the tranny downshifting.
It's just not as precise as the old foot.
 

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That is true. If you give it some thought, you probably add some accelerator pedal sub-consciously knowing that you are going up a hill. All the cruise control knows is that it is slowing down, and that it needs to accelerate in order to maintain it's set speed.

You will feather the pedal for a smooth increase in motive effort. The cruise will probably not even start to apply accelerator until it has dropped 1 or more mph below it's setting, and therefore is already behind the "eight ball". Add the increased weight and wind drag of a 4000+# trailer behind you, and that only compounds the issue. I only use the cruise when in level terrain while towing.

Tim
 
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