When I tow my popup camper should I turn the O/D on or off? I have a 2005 F-150 4x4 with the 5.4. I think fully loaded the camper weighs 2,000-2,500 lbs.

 

that aint much weight at all. I would say if you can keep it from shifting in and out of overdrive once you hit your desired speed you should be fine. that is, if you get to your cruising speed of say 65 and your truck keeps downshifting a lot, turn it off, if you can get it into OD and keep it there, I would say you are fine. That's just how I would approach it and have approached it in the past.

 

Is there a mpg benefit if i can keep it in overdrive while towing?

 

You should not have any trouble keeping it in 5th/OD. I pull a boat approx 2000 lbs with trailer with my 4.6 2v and it idles under 2100 rpm's going down the interstate at 70 mph and I still average over 20 mph according to my edge. I never turn the OD off except maybe when I head up to Boone/the Mountains here in NC. I imagine the mileage will suffer with it not in overdrive but the truck should be more powerful. Its kinda your preference.

 

I agree with what was said above. You shouldn't need to turn the overdrive off. It should have enough power to get into overdrive and stay there.

 

I am not a mechanic so I hope I don't sound too dumb. But am I right in saying that the reason people turn O/D off when towing is because of excessive shifting, not because of towing in O/D is bad, right?

 

pretty much. If the weight is too heavy the truck will keep trying to downshift, then shift back into OD, then downshift,etc....that is really hard on your transmission. I have pulled a 14' enclosed trailer a lot, no idea of the weight, but it catches a lot of wind. Sometimes when it is unloaded, if it not windy I can run in OD, if I am bucking a headwind, then I have to turn it off. IF it is loaded with a lot of weight, I pretty much always have it off. Your pop-up shouldn't catch much if any wind, since it is low to the ground. And yes, you will get much better mileage if you can run in OD since your engine is not revving nearly as high.
Usually if there is any question I err on the side of caution and turn it off. But in your case as the guys said before, I think you will be able to run overdrive and keep it comfortably in OD with no problem. Remember an occasional downshift like when passing someone, or on a hill or something is fine.