What is the difference between a "shift solenoid," and a "speed sensor?"
 

My Ford: 2001 E-350, Econoline, V10

After a long trip, my van's automatic transmission is shifting rough, revving up before the first shift point.

I ran a diagnostic, and it came back with two codes: one that said check fluid level. I did, and it was ok. The other code said "speed sensor."

When I called the Ford Parts Department at the local dealership, they had a "shift solenoid," but no speed sensor.

A shift solenoid sells for $412. A speen sensor sells (at the local NAPA) for $42.

Anyone have any idea which part I might need?

Thanks

The best I can try to answer is, the speed sensor provides the info for when to shift , the shift solenoid causes the shift to take place.
The solenoid may be part of a solenoid assy that contains the solenoids.