I just returned from a 6,200 mile trip to the west coast in my 08 4.6L RCSW pulling a 3,500 lb. trailer. We did a lot of climbing. The motor was great and I averaged 14 MPG running 65 MPH. The biggest problem was gearing. With O/D on, the truck did a lot of downshifting. With O/D off, the truck ran in third gear, rarely had to down shift, but ran around 2750 RPM. The gear ratio between 3rd and 4th is very wide and I was wishing for a gear between the two.

I ended up running in 3rd gear all the time. It seems to me the transmission shifts better and maybe slips less with O/D off. Can anyone confirm that? I've concluded that I need to lock out 4th any time I pull my trailer, even though the higher revs probably uses more fuel.

 

The owners manual agrees with you:

http://www.fordservicecontent.com/Fo.../08f12og1e.pdf

To eliminate excessive shifting, use a lower gear. This will also assist

in transmission cooling. (For additional information, refer to

Understanding the gearshift positions of the 4–speed automatic

transmission


in the Driving chapter.

 

my 2005 with the 5.4 does the same but in 4th gear instead. I usually turn the O/D off when im hauling on a road that's hilly. if the road is relatively flat and you can get up to speed and get to where it would stay in O/D then I would keep it off. but with the smaller 4.6 and 3500 lbs you might want to keep it off. it does burn more gas but it will save your tranny.

 

Unless I'm missing something, an '05 with "O/D OFF" is limited to its first three gears. O/D is fourth. Thats how mine is anyway. With regard to the original poster, yes it does need another gear in the lineup. Our '10 Expedition had a 6 speed auto with a bona fide tow/haul mode and I really liked it.

 

You are correct; our trucks (04 to 08 at least) are 4 speeds, but the O/D IS the 4th speed.

If we are complaining about not having a 6 speed automatic, then go further, as the Dodges (and others) now have a 9 speed I believe.