2004 Chevrolet Silverado 1500

I CURRENTLY OWN A 2004 CHEVROLET SILVERADO 1500 SERIES. OVER THE PAST MONTH THERE HAS BEEN A VIBRATION IN THE TRUCK. IT DOES NOT VIBRATE ALL THE TIME, BUT WHEN IT DOES IT IS VERY NOTICEABLE. IT USUALLY VIBRATES AT SPEEDS FROM 45 MPH TO 70 MPH. I HAD REPLACED THE ORIGINAL TIRES ABOUT THREE WEEKS AGO AND THAT DID NOT HELP. I'VE HAD IT IN THE DEALERSHIP THREE TIMES IN THE PAST THREE WEEKS. THEY REPLACED A REAR U-JOINT, WHICH DID NOT HELP. THE LAST TIME IT WAS IN THEY TOLD ME THAT THEY CAN NOT FIND WHAT IS WRONG WITH IT SO IT HAS TO BE MY NEW TIRES. (MY TRUCK HAD THIS VIBRATION BEFORE I PUT NEW TIRES ON IT AND I TOLD THE DEALERSHIP THIS.) THE DEALERSHIP ALSO PUT OVER 400 POUNDS OF WEIGHT IN THE BED OF THE TRUCK AND THAT DID NOT MAKE A DIFFERENCE IN ANYTHING. I'VE ALSO HAD OTHER NUMEROUS PROBLEMS WITH THIS TRUCK. BRAKES, TRANSMISSION, STEERING ARM. I BELIEVE THAT THIS TRUCK IS VERY UNSAFE. WANTED TO FILE A CLAIM HOPEFULLY TO AVOID MORE SERIOUS PROBLEMS. HAVE CONTACTED LEGAL ADVISE REFERENCING THE LEMON LAW. *JB