Ford Excursion :: V10 4r100 Transmission - RPM Dropping When Climbing The Hill

Today I was 160 miles into a 250 mile drive and things were going well. I was cruising at about 75-80mph and approaching a fairly long hill of moderate grade. As I climbed the hill, my rpm was dropping, as expected before a downshift. The downshift never happened. I kept pushing more pedal and eventually, at maybe 40mph, it downshifted, but still no power. Engine being held at around 2500 rpm. No power no matter how much I pushed. Down hill I was able to resume speed but as soon as the next uphill, same thing, no power, no shift. Pulled over, it was raining hard. Checked for wet fuse box, control modules, pcm, wiring harnesses, everything dry. Checked all fuses. Disconnected battery in hopes of forcing reset, no change.

Checked trans fluid, it was clean, red, full, and unburnt. No visual wires broken or chafed. No odd smells or sounds. Nothing noticeably hot. Truck hits 45mph max on flat ground. I limped it this way for 20 miles. If I push my foot to the floor to really force a downshift, engine will rev freely up to redline with no resistance once it downshifts. If I let the rpm drop down, it will catch and lock back in. Now when I come to a stop the truck has a very lopey and rough idle and will stall once I come to a complete stop. It will stay running if I give it gas. In neutral and park the engine still has a lopey idle and is rough. Will possibly die at times. Sounds smooth and perfect when you rev it in neutral or park. Reacts as it should with no hesitations. No check engine light and no flashing OD light. Will shift into all gears, just moves through them with no power. Let truck sit for 3 hours, issue remains.