Yo! Steve H!
I hope you don't mind me picking your brain.
'05 Expedition, 5.4L, 128k, trailer-tow package.
When driving (trailering/loaded or unloaded), uphill, the vehicle does not maintain speed. It continues to slow while I add more throttle, until it slows to around 40-45MPH when it finally downshifts.
I can press the accelerator down faster (before it reaches 'degraded velocity'?), in an effort to get it to downshift, but it doesn't seem to be the right answer for this situation.
I recently replaced both lines from the transmission to the cooler & radiator (rusted through, sprung leak) that required removing the radiator (and the quick disconnect fitting on the radiator) so I'm wondering if I may have an obstruction somewhere in the fluid path.
Referencing the FSM doesn't seem to help clarify troubleshooting required for this particular issue. Any guidance is appreciated!