This is on a MOntana. The front passenger strut pops while the wheels are being turned left/right. I see the coil twisting when the wheels are turned. That makes the popping sound. I sprayed wd40 thinking that would make it slide instead of popping but odesnt work. Does that mean a bad strut?

I am thinking maybe the strut bearing is causing this #6 in the illustration. Take it to a reputable shop that does front end alignments and have them check it out for you. I will attach an image of the bearing.

http://files.automotiveforums.com/uploads/655404bearing.jpg

Well i took it to the GM dealer.They said it needed a new strut. But wanted to charge me $400! I called another tire/brake place and said it would cost about $160 to replace that one strut. I was wondering if i could do this myself? i usually do maintenance on my vehicles but never did struts before. Does the sprint need to be compressed? Or is it a unbolt, remove, replace, rebolt thing? thanks

Yes you will need a spring compressor tool, and usually the replacement of a strut will require an alignment, becuase the posistioning of the strut affects the camber and caster adjustments.

I'm gonna leave it up to the pros on this one.;)