2002 Ford Excursion P0720 and Flashing O/D light

Transmission problem
2002 Ford Excursion Two Wheel Drive Automatic 144500 miles

My 2002 Ford Excursion V10 has recently been having some transmission problems. When I put the truck in reverse or even sometimes when im taking off slowly in drive, it will die. This does not always happen, but it is more prone to doing it when the transmission is warmed up. The code is for a Vehicle Speed Sensor input/output. I change the VSS and and I am still having the same problem. It almost feels like the torque converter is temporarily locking up and stalling the truck out as if it were a manual transmission and I let the clutch out in first with no throttle. The Ford dealership told me it is a transmission electrical problem. Any ideas? I heard something about the Digital Transmission Range sensor being a common problem in the 4R100 trannys, is that the transmission I have? Another service shop also said it might be the torque converter or lock-up converter. Anything will help. Thanks a bunch.