At what trailer weight do you turn off your transmission over drive?

 

That's a difficult question since you don't say what you're pulling or where ie mountains or flat. But I'll tell you how my Dodge trans works. I pull a 8,700 bumper pull toy hauler out west and my 48re trans does just fine in OD. My old Dodge (2001) did too with the 47re. Unless my speed got down to where the trans temp guage got over 180* I always let the transmission decide where to shift and just left it in OD. If you don't have a trans temp guage that is the first thing I would strongly recommend for anyone towing with an auto. I've found that the Dodge transmissions don't overheat except when going under 30mph and pulling uphill then the temp will raise above the norm which is about 140*. A guage is cheap compared to the price of a rebuild IMO. I can't answer for your Ford but wouldn't be surprised if is similar to Dodge for pulling, a Ford specific forum may better answer your question but on any automatic trans heat is the main killer with performance enhancements second.

 

I only turn mine off if it is a heavy load. My boat i leave it in od. The 45p new holland i leave it in od, but our dozer, back hoe, and 95hp new holland, big load of hay 15+ bails and our big john deer it gets locked out. Every thing but the boat is on a 32ft gooseneck.
That should give you an idea weight wise. Your truck will go into od if it says towl haul on it I run it mostly because it helps me stop better.
My trany runs around 160-180 empty have towed anything since i got the guages in but I havent been able to get it over 180 so thats good.

 

Gotta depend somewhat on what transmission you have, and how you're geared. Plus how much aero drag the trailer has. A basically flat little 18' utility trailer has dang little drag compared to a boxy camper trailer. Some transmissions really do have a weak OD, while others are strong enough for towing in 5th.

 

On flat ground tow in overdrive going thru the hills mountains I leave mine in od but once it down shifts I turn it off as so it wont hunt in and out of od.

 

i've hauled as much as 33,000 total, and left the overdrive on and did 70mph. depends on the truck, trailer, load etc. there is no set rule. but if you are hauling up and down a lot of hills around 45-60mph, might be best to just let it off...