Ok..SO here is the deal. I have a 2001 4x4 2 door blazer. The left front tire was wearing out on the outside and I used to have to steering wheel turned a bit to the right bc it pulled to the left... I just put new tires on (NextonMud terrains P235 R15....) which were the same size as my last tires (Goodyear AT Wranglers...walmart)... when I got the new tires put on I drove and noticed that it began to pull to the right. If I hold the steering wheel straight my good.blazer willpull quickly to the right( duh)....I had the techs switch the two front tires to see if that would straighten it up..It didnt... Next They told me I needed a new idler arm. I went and got a new idler arm and then got a front end alignment....It didnt fix the pull problem..When Im on the highway I have to hold the steering wheel to the left and if I make even a nudge of movement to the left I here something making a significant "humming/vibration" noise..I think its the tire....Any clues as to what the heck my problem could be...??

 

Did you get the printout from when they did the alignment? I believe some people can look at a printout and tell if it's a good alignment or not.

 

Possible wheel bearing. Mine was doing almost the same thing and that's what it was. I don't know what year yours is but mine is a 2000 and I've replaced 2 in the past 2 years. Each time there was almost zero play in the tire, no matter which way I tried moving it. (hence your front end alignment not failing). Either way it's a possibility that I just figured I'd share

 

Sounds like a case of worn out ball joints and perhaps cv shafts and hub bearings. Not too hard of a fix if you have the right tools. I just got done doing this myself and my truck handles better and drives smoother when on the freeway. No more high speed vibration.

 

*Moved to 2nd Gen Tech*