1990 Chevrolet Suburban

LAST WEEK NOTICED VIBRATION (SHDDER) COMING FROM THE FRONT OF THE VEHICLE. THOUGHT IT WAS THE TIRES OR BALANCING. REPLACED ALL FOUR TIRES (EVEN THOUGH THEY WERE NOT WORN OUT). STILL HAD SHUDDER, SO NEXT DAY TOOK IT TO CHEVROLET DEALER IN LIVERMORE. TOLD HIM THE SYMPTOMS AND MADE AN APPOINTMENT FOR 6/29/99 TO HAVE IT CHECKED. SERVICE MANAGER ASKED IF THE VEHICLE HAD OVERDIVE, REPLIED YES, HE RESPONDED IT MAYBE SOMETHING IN YOUR TORQUE CONVERTOR. NO DOUBT WILL FIND OUT. THEN CHECKED WITH A FRIEND IN MN WHO ALSO HAS A 1990 SUBURBAN. HE ASKED IF IT WAS HAPPENING AT ANY PARTICULAR SPEED. I SAID I NOTICED IT WHEN ACCELLERATING UP FROM 45 MILES PER HOUR. HE THEN ASKED IF I HAD OVERDRIVE AND I SAID YES. THEN HE ASKED IF IT HAPPENS IN THE DRIVE SETTING, SAID I DID NOT KNOW. CHECKED THIS OUT AND THEIR WAS NO SHUDDER IN THE DRIVE POSITION. I BOUGHT THE VEHICLE WITH FULL WARRANTY IN NOV/DEC 1991, IT WAS A GM EXECUTIVE VEHICLE. AT APPROXIMATELY 33,000 MILES THE ENGINE LITERALY BLEW UP AND WAS REPLACED UNDER WARRANTRY. AT APPROXIMATELY 36,000 MILES THE TRANSMISSION FAILED AND AGAIN FORTUNATELY IT WAS STILL UNDER WARRANTY. MY FRIEND IN MN ADVISED THAT HE ALSO LOST HIS TRANSMISSION UNFORTUNATELY OUT OF AND WARRANTY AND HAD IT REPLACED WITH AN AFTER MARKET TRANSMISSION UNIT FOR THIS MODEL THAT DOES NOT USE / HAVE THE OVERDRIVE FEATURE. ACCORDING TO HIM THERE WERE MANY FAILURES OF THIS O/D TRANSMISSION UNIT AND HENCE THE AVAILABILITY OF AN AFTER MARKET UNIT AS DESCRIBED. HE SAID THE O/D FEATURE WAS DESIGNED IN TO MEET GOVERNMENT MILEAGE REQUIREMENTS AND CLEARLY HAD PROBLEMS. I WILL KNOW TOMORROW WHAT THE DIAGNOSIS IS, AND IF IT TURNS OUT TO WHAT MAYBE A DESIGN THAT DOES NOT PERFORM AS DESIGNED (DEFECTIVE)AND THERE IS DATA TO SUPPORT THIS THEN I WOULD LIKE YOUR GUIDANCE AND OR SUGGESTIONS ON AN APPROPIATE WAY TO APPROACH GM TO CORRECT THIS AT THIER EXPENSE. PERHAPS ALL THIS NOTE IS REDUNDANT AS THEY (GM) MAY ALREADY HAVE A POLICY ON REPLACING THESE UNDER WARRANTY. THANKS FOR YOU HELP.