how do you know when the turbo goes on a 96 f250 psd?

 

It wil rattle or throw parts in the motor. You can catch it earlier by inspecting. Remove the intake hose and grab the wheel to see if there is play in and out and up and down. Look at the fins. They should be shar and not worn down. Look to see if they look like they have been sandblasted.

 

Yea, everything should look almost freshly machined.

I believe there will be a little iddy biddy play, but a lot of play is bad.
You shouldn't be able to wiggle it much at all if you can move it any. If it moves a lot, its def bad.