Truck shifts into 2nd gear

During first 10 minutes of driving (any weather), if I have to slow down or brake before truck shifts into 2nd gear (in traffic or turning corner), it will hesitate; when I accelerate, it jerks forward with clunk. After 10 minutes warm-up and running, truck has no problems. Problem has been going on about 6 months. Ford dealer scanned transmission and found no problems, dropped pan and replaced pistons, servos and fluid; this did not fix problem. Had defective throttle body replaced years ago; gas pedal is sticking again.