We have an 2003 F-150 4x4 FX4 that won't go forward, but when we push it up to 30kph it drives and shifts fine?
Sounds like the transmission has a problem. have a tranny specialist check it out.
Sounds like the torque converter is shot.
Is the o/d light on the dash flashing?
It is probably not going down into first or first is slipping bad. Or worse there is a trans fault and it is defaulting to 3rd. You need it to get checked out by a trans shop. Chances are the torque converter was able to compensate for this but it too may have gone out due to being over worked
Looking for a Used F-150 in your area?
CarGurus has 207,247 nationwide F-150 listings starting at $1,990.
Search Ford F-150 Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Ford F-150 Experts