'04 GMC Steering Issue
 

Have an '04 GMC Sierra 1500 4WD w/ 80K. When cold, steering will not turn to the left without a lot of effort (like no power steering at all) for the first one or two times, then all is fine, until it sits and gets cold again. Turning to right cold or otherwise is OK all the time. Had the P/S fluid changed out and that didn't help. Any suggestions? Hate to just start throwing parts at it, that can get expensive really fast.
Thankls