It's likely out of adjustment and an easy fix if you can get to it without breaking the selector cable. If you break that cable, know that one of our members is making those....alias thisoldtruck, I think. You'll have to remove the gauge cover and the plastic cover underneath that wraps the steering column. With that exposed, you'll understand what needs to be adjusted.
John
"Blackie" - 1986 F150 4x4 - Mildly warmed over 351W HO - Original owner