For future reference, that vibration is a tread separating. I've had tread separations (three on one vehicle, one hot weather trip) and they usually start getting out of round enough to feel when the height of the bubble is as little as 1/4 inch. This is often long before a big chunk of tread lets go.
My experience also is that these are not blowouts. First the tread separates and flies off, and if you keep going long enough (as truckers might do on a trailer tire) the tire body then collapses from running without a tread.
Blowouts on modern radial tires are usually zipper failures in a sidewall, and those give no warning at all.
There are high pressure (up to 80 PSI) rubber valve stems adequate for normal loads on this class of truck chassis, and the factory usually installs them OEM. That's not the same stem used for a car or a truck with passenger car tires. The tire store should know the difference.
The high pressure rubber stems should not be used with any type of extension, or accessories like screw-on pressure measuring equipment. These are actually metal stems surrounded by a rubber body, and if allowed to flex, you will have fatigue failures on the metal part (which was not a problem with passenger car rubber stems).
If you are going to use extensions, install short stainless steel stems. If you want the best solution and do not change tire positions, get long metal stems fitted to the application. Even these, at least the inner dually stems, should be supported at the outer ends, a good kit includes that supporting hardware or grommet. If long metal stems flex, they'll eventually fail from fatigue.
