Tire Related Problems of the 2000 Suzuki Vitara

Tire problem

Since date of purchase, while driving vehicle developed severe vibration presumed from transmission lasting approx. 10 miles, afterwhich vehicle resumed somewhat normal performance. Dealership could not determine cause. It is now 2,000 miles later and vehicle constantly vibrates and worsens as speed increases. Dealer rebalanced tires - test drove and told me vibration was still there. Mechanic cannot determine cause of vibration. Was told vehicle is safe to operate. Still awaiting a diagnoses from dealership.