This is a very common problem.
It could very well be the seat and socket.
I invented a super duty seat and would replace both the seat and socket first.
It is listed in the transmission rebuilding section and costs less than the dealer part
To remove the trans handle shifter;
Carborated G54 trans--pull up on the handle boot and then push down on the double D handle retainer ring and turn it counterclock 1/4".
EFI W56 trans--pull up on the handle boot and remove the four 10mm head 6x1.00mm bolts.
If the seat and socket are good, then you may have a worn 1/2 fork and/or worn mainshaft bearing. With 220K, it sounds like a trans job might be next.
Marlin
