i have a 1996 SE7 and the rear rubber vibration (u-joint) goes out in about 8000 miles. it doesnt go off road ever. nothing broken. as far as i can see everything else is ok. I hope someone can shed some light. thank you

 

Its called the flex coupler, also called a roto flex.
If you are using cheap ones they will not last, if you are installing it backwards it will not last, if you have to much suspension lift it will not last.