steering noise ?????

i have a 99 sierra that is making a noise while turning either direction(while sitting still or moving). it would stop if i accellerated a little, but now it does it either way. when the wheel is turned, the steering lines vibrate and get worse on accelleration now. thought it may be the power steering pump but not sure. does anyone have any suggestions or trouble shooting tips to narrow the fix?
thanks in advance. tim

Sounds like the pump but open the hood and have someone turn the wheel and listen.

thanks for the reply taillight. will try that when my little helper(my son) arrives. take care. tim

I had a similar problem with my 2000 GMC, Everytime I turned the wheel to the left it sounded like a dry ass rubbing against the side of a bath tub.

I took it to the dealer and they replaced the power steering pump, pitman arm, etc. No problems since.