I have a 2002 7.3 F350 XLT extended cab long bed single rear wheel that I bought new in 02- I maintain it immaculately and all maintenance is done by the book. It is all stock except for the Donaldson Blue 6637 air filter- the transmission started to flare and slip at 73,000 miles so it was replaced with a reman tranny by ford- while it was still under warranty it started to flare again so it was replaced with another reman tranny by ford at 98,000....it now has 112,500 miles(I don't drive it much)- it seems to run well and get between 14-15 miles per gallon, starts easily with no issues but noticed a few weeks ago when pulling my 5000 lb travel trailer in the mountains, when I would come up on a hill I would get to about 60 mph at 2200 rpm's and would find that my foot was on the floor....the tranny seemed to shift ok(up until that point)....the truck seemed to be running smoothly up until I got to a hill, then it seemed to not downshift into the lower gear- I could manipulate the gas pedal by punching it a little at the base of the incline to get it to drop into the lower gear but that is not how I drive, I drive with a soft smooth foot- I have never had to do that in the past, although I don't tow a whole lot I have used this truck in the past(5 years ago) to tow 10,000 lbs and it performed well shifting smoothly in very mountainous regions and can't understand what the problem is...(when I calculated my gas mileage at fill up it was crappy- 10.4...I usually get about 12)..I tow with overdrive OFF, there were no warning lights on the dash and the engine and tranny temp stayed normal....I am just sick about this hoping that the tranny is not failing AGAIN. I dropped the truck off with my Ford Mechanic on Tuesday and told him to keep it as long as he needs- it is now Saturday and haven't heard anything yet- I like to educate myself as much as possible with issues with my truck- did research all over the internet and YouTube and many people suggest dropping the fuel tank and cleaning the strainer cartridges and replacing the pickup screen/foot....I instructed my mechanic to do this(whether or not the current issue has anything to do with that) The fuel tank is a 38 gal plastic tank and I never use any fuel additives….does anyone have any thoughts or ever experienced anything like this....does it sound for sure like it could be the tranny or could it possibly be something else?? People rave about theses 7.3's and they can yank the side off a building but I am having this issue pulling this puny little travel trailer....and after being SO mindful about the care and maintenance of my truck I am feeling quit discouraged....I know I need to be patient and wait for the mechanic to call but was wondering in anyone had any input or ever experienced anything similar and what they did to fix it. Thanks!