OK, not quite sure what's going on but all of a sudden out of the blue my power steering is very jerky. It like comes and goes in the middle of turning and after a turn when you would normally let it go back on it's own, it doesn't. And yes the fluid level is good. H E L P !!!!!

 

Your lower shaft u joint is rusting to the point the bearings are no longer smooth. Do a search on these forms. Lots of threads about this.

 

Hmmm, NY roads in the winter (salt) and beach driving in the summer (salt water & sand)

 

Here is a pretty decent price for one with free expedited shipping. Im literally about to order one right as I saw this thread.

http://www.ebay.com/itm/04-08-F-150-...|Model%3AF-150

 

RockAuto is less expensive.

 

In the meantime you may be able to help it with some PB blaster or something of the sort to break up the rust and help lubricate it.