Ok I noticed lately well right after I bought a 7x16 x7' tall enclosed double axle trailer that my truck jist won't GO! From a stop light and such the 5.4 is fine the 4.30 gears are the big plus here. My main problem is highway and when i feel the truck shoukd downshift it simpky will not. Im in new jersey so most of my travels are local but I do get onto I295 for short distances and ANY over pass or decent gust of wind will take me from 65-70mph cruising speed and drop me to 60nph very quickly...so I'll have to put my foot deep into the accelerator which shouldn't happen with a trailer that I have at the current time maybe 1000 to 1200 lbs of tools in it. I k ow I only have a 5.4 bit it shouldn't be that bad right? My main concern is the freaking tranmssion WILL NOT DOWNSHIFT if I'm anuwhere from 2nd through OD and I go to pass so.eone on the highway or merge I to traffic or simply go to speed up from a 30mph road intona 45mph road the truck will either a- droo out of OD and stay in 3rd but lug itself at 40nph with little rpm or if I'm cruising at 36mph in 3rd with the tq locked the truck will just unlock the tq converter BUT still stay in third and lug itself in till 45mph when the revs finally start building from speed? If I manually drop the gear selector the truck does what I make it drops into 2nd jumps to 3k and just builds power and speed like it should and goes! But if I let the computer control it it simply acts like a underpowered v6 and won't pass a snail in a race.
something had to be wrong if it's sone type of sensor or could it be my truck was factory 5.4 with 3.73 gears and I had 4.30 gears added but kept the stock computer so it's all glitchy and not in synch. I need to fix it for one I tow this trailer ever day now for work and this week I'm adding wood shelves so I can add all the tools I need to have which is even more weight and Saturday I need to go pull my dad's 33ft camper home and I'm dreading the 7400lbs that's gonna be hooked to my truck

 

How old is it? Transmission fluid full and clean? I have a 2006 5.4 that I put a tuner on - made a huge difference; much peppier and quicker throttle response.

 

What miles? Time for a tranny fluid change?

Try double-pumping the gas. WOT, let off, and punch it again. That might give the tranny a clue.

Vacuum leaks.

Tuner.

 

My signature is t showing up? 2004 f350 with 160k, trans has been completely rebuilt less than a year ago. New plugs 1.5 years ago with new cop boots, air filter just changed along with fuel filter, cleaned mass air and throttle body last week. Not a trans fluid issue seems more along a tuning problem

 

No vacuum leaks from what I can tell, no tuner installed

 

Signatures don't show up on mobile.....