The big truck seems to have some tired steering going on these days. (1990 F350 Quad Cab / 2wd). I know the belt isn't slipping, nothing is leaking, but the symptoms don't line up with anything I've dealt with before. It's fine if the truck is moving at anything more than like 1 mile an hour. RPM's of engine don't matter either if it's not moving, I could red line it. There is just a faint vibration, almost like what a hydraulic 3pt hitch feels like on a tractor when it's slightly low on fluid and it's grabbing an air bubble as it moves the piston repeatedly. Fluid is full though, looks clean too. I wasn't sure if there is anything to check on the box or if I should just change the 33 year old original power steering pump and see what happens. I'm just sad I can't put one of my 300 straight 6 pumps on, I love the fake supercharger whine lol..