Boots don't have to be bad for axles to fail. My driver's side boots looked Ok, no tears or rips, but the inner joint was failing. Symptoms were as you described - vibrations at highway ( and sometimes lower) speeds.
I also inspected the driveshaft - flex coupler and centre hanger bearing was worn, also trans / transfer case mount had cracks in the webs.
Point being that it may not just be your axles causing the vibrations...
Last edited by lgb240; 04-12-2014 at 09:38 PM.