[big gear head]

I had a rear end shop for 15 years and most of the time when I would swap gear ratios in a car from a 2 something to a 4 something the customer would complain about a vibration caused by the rear end. It was not the rear end causing the vibration. A drive shaft is designed to run at a certain RPM. When you change gear ratios the drive shaft RPMs change, and a 4.10 will spin the drive shaft a lot faster than a 2.73. When you exceed the limit of the tube it will develop a bow, which causes a bad vibration. The cure is a thicker wall tube or a larger diameter tube. If your drive shaft bowed at that speed then it could have easily broke the tail housing.