My 94 awd astro has 116,000 on it. Its on its 2nd front diff and at speeds over 70 the front end is shaking real bad and the front diff has now started to leak at the drive shaft seal on the diff. Since I have had to change out both tortion bars with shorter ones the driveline seems like it binds. Full left turns can even kill the engine. My thought is the drive shaft is out of balance or bad u joints and the tortion bars are set to high but the vibration was never this bad until we went on a trip fully loaded. And could only do 65 mph and smell the diff oil burning on the exauste. All the tire were recently ballanced and a fresh oil change was done but nothing to the differantial was done. Please help.