Suburban :: Shakiness While Accelerating In Passing Gear At Highway Speed

I just had four new LT E rated tires installed (balanced). Alignment is good and did not require adjustment. Tires are correct size for the vehicle. I noticed during an extended highway trip yesterday that the truck (94 K1500 Suburban) seemed to shake or rather bump slightly when I was accelerating to pass in the sixty-five to seventy-five mph range. Almost seemed like driving on a fine washboard. I looked at the balancing weights which on three of the wheels appear to be nearly the same size. Then I noticed the right front weight is obviously larger than the other three. Could this be the problem?

There's a bit of a story here. (Isn't there always?) I bought the tires from one source (whom I would never trust to do any repairs) and had a shop I deal with regularly close to home install them. The morning after the install I went to check the pressure cold and discovered that the right front tire was a standard tire while the others were the LTs which the bill showed I had paid for. So I missed this when I bought them (they threw them in the back of the truck after assuring me all four were the same) and my mechanic missed it when they were installed. Now the tires do look almost identical but the lettering on the standard tire was black both sides while the LTs were white on one side. Of course the standard tire has a lower maximum psi rating.

I went to the mechanic first and he admitted to noticing this but I guess it just didn't register with him to double check to see if it was actually a different tire before mounting it?! I should say I am having second thoughts about using this shop in future, especially after they under inflated the tires at 30psi as well. When I told him I was running 45psi he looked at me like I was from Mars but then, upon checking his Mitchell Manual he says that yes, this truck should have 45 to 65 psi. Anyway, the guys who sold me the wrong tire made good on the problem however they installed and balanced it and I'm wondering if they got this part wrong hence the vibration I'm getting at around seventy-five.

The work order from the guys who installed the tires also states I need two upper ball joints, pitman's arm and left outer tie rod and alignment (which I understand is standard when doing this job). Now I had them show me this and while I'm no mechanic I could see the play in the ball joints was extremely minimal and pitman arm almost negligible (the mechanic had a lot of trouble showing me this had any play at all and admitted he had seen much worse). The boot on the left outer CV joint is also split and missing its grease. I'm not saying the suspension is perfect but I think they are on a fishing expedition here and I am skeptical this is what is causing the vibration at high speed because I never noticed it until the new skins were applied.