2001 f-150 4.6 L automatic trans. slips in just about every gear and shift lever wont go into the Park position .I had the tranny serviced not too long ago(drained/filtered)
Could be the park pawl inside the tranny being misaligned or broken. You could try disconnecting the shift lever at the tranny and trying manually to shift it into park. If you can the problem is inside the column.
Search Ford F-150 Questions
Ford F-150 Experts