I feel your pain.
This could be a number of things, you will need to check for trouble codes (it could be a transmission or engine sensor, likely ECT). Then you will have to have the line pressure tested.
I am waiting for a new Valve body for mine (my valve bores were too worn out to just replace the valves. My converter bypass valve and pressure regulator valve caused my problems. No TC lock up and failsafe mode (bang shift).
The valve body on our tranny is a weak link.
It??s not a good idea to drive around (especially highway) with a tranny that won??t shift to overdrive. It can cause the tranny to overheat and do serious damage. Also, if it starts bang shifting stop driving it. Ford thought (a better idea) that if any problems developed in the tranny, they would engage ??failsafe? mode and stop the flow to the cooler.
Driving with bang shifts = totally blown tranny
jeff
