I'm guessing the lever is a little loose and wiggles. What I did was go to ford and get a diagram of the colum and shift leakage from the parts counter.
the first the to try is the two screws at the bottom of the colum under the dash where the cable connects to the shifter, these screws come loose every now and then.
second would be check the bushing on top of the colum that the shift mech. runs through sometimes the tube the shaft runs through breaks it like $25 from ford and the bushing are like $3 apiece if this is the problem you mostliky would would replace the the inner shaft as well for $12.
and third I would pull the gauge cluster out while you have the colum dismantled and it easier to get to and pull the gear indicater out and pull a little more tension on the spring, with the truck being in P R D most of the time the spring never gets to comprese so it loses tension after awhile.
Sorry for the grammer and if you couldn't tell I just did this all last weekend. good luck hope that answers you questions
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