I have a 2005 F-350 6.0 liter diesel crew cab. I've started to notice steering problems recently (66K miles) which happens intermittently. Almost feels like very low tire pressure, loss of power steering, pops to left and to right when trying to drive straight. This has happened 3 times in the last week and will go away after a few minutes. Steering fluid is full. Any ideas what could be causing this?