have a 78 w-150 with only 350,000 miles on 'er (and going strong). a couple months ago, the steering started getting way loose so i consulted the FSM, and did all their tests in there for loose steering to no avail, so i replaced the steering box (its power steering). its been four months and ive replaced it three times now, but the steering has barely improved. it will be nice and solid for a few days, and then back to the same old s***. there is at least a 1/4 turn of play in the wheel before it hits any resistance. anyone know what the problem might be?