First, I just want to say that I have read many threads on this issue with the Blazer but everyone's situation is different so please, any advice would help...
Ok, Like many other people here, I have a problem with vibration. It has never occured during braking so I do not think it is a warped rotor... I generally happens at 67-90 MPH on the highway but strangly, after 90 MPH it goes away, but it seems to be the most severe at around 80 MPH.
I purchased the vehicle in Sept 2004 with around 56,000 miles on it from a Chevy Dealer who reassured me that it has had a 100+ point inspection but did not give me any sort of written guarentee that there had actually been any sort of inspection performed (I should have insisted that the dealer provide me with written results of the inspection...)
My first vibration problem with the vehicle happened a week after I bought the car and after 62 MPH, it felt like the rear-axle was about to fall off! I inspected the vehicle and found that left-rear wheel was missing it's wheel weight so a simple balancing fixed that issue.
October 2004, I hated the top-heavy feeling when turning so I had the car lowered with a 2/3" kit... After the installation, the mechanics called me and said my front hubs were shot and they could not properly align the vehicle without new hubs... I foolishly paid for this shop to replace my front hubs, costing roughly $1,800. I will admit, I am an idiot for paying this shop to do the work and will never EVER go to them again for anything! I can't believe how stupid I was for trusting their opinion and not taking (towing, pushing ETC) my car to another shop. STUPID STUPID STUPID...
December 2004, Replaced all 4 tires, balanced and went on driving... No vibration problems...
Summer 2005- At about 70k miles, mild vibration started to occur at highway speeds... No noise, just a little vibration.
Fall 2005, vibration getting slightly more noticible... Felt like upgrading the look of my ride so I purchased 18" wheels with high-performance tires (Yokohama ES100). Figured that this would help with traction and eliminate the wheels from the possibile list of likely suspects... Nope, same vibes at same highway speeds...
Feb 2006, started noticing that the front-left tire was developing wear on the inside edge which to me was symptomatic of the alignment going bad. Had the front-end realigned along with a tire rotation and re-balanced the wheels once again... Same vibration...
Mar 2006, Noticed that my front-left tire is wearing on the inside edge is wearing once again and the vibration has not changed it's "location", it seems to come from the same place at the same speeds 67-90 MPH. One note- when the vibration occurs, I can feel it in the steering wheel which I believe means the problem is in the front of the vehicle. Also, when the vibration happens, I can see the front RIGHT-HAND side of the car shaking- which is strange because my front-left tire is wearing...
I was originally going to through new U-joints at the problem but now i'm getting more convinced that the problem is one (or both) front wheel bearings going bad again. I now have 86k miles on the vehicle so it's been about 30k miles since the hubs were last replaced or serviced...
What I plan to do in the immediate future-
Replace U-Joints (I already bought the parts, might as well replace them).
Have a brake job done at a reputable shop, have the front wheel bearings inspected (while i'm watching) during the brake job...
I hope it's not the damn bearings ($$$)...