i just bought a 99 f250 super-duty and the transmission when u put it in drive
it wont go you have to build it up to around 4 thousand rpm before it will
budge. it will go great in reverse...and idea
Actually sounds like the tranny is almost shot, what does the fluid look and smell like? If it's dark and smells burnt you can bet it's on it's way out completely. But if the fluid is still a nice red color then it could be a control module or solenoid problem, a good tranny shop will be able to plug in and runs a series of tests and then tell what is happening and what it will take to fix the problem.
Search Ford F-250 Super Duty Questions
Ford F-250 Super Duty Experts