GM-GMC: 77 chevy driveshaft, rear end, best interest

Question
i was driving down the freeway about 65 mph when i heard a very heavy grinding noise the grinding continued til i got to the side of the road and parked. I looked underneath the truck and noticed that a sweatshirt got wrapped around my driveshaft. i unwrapped it and drove home eperiencing minor vibration. What parts would be effected and what was grinding so bad?

Answer
I am not sure what might have caused the grinding noise, but it sounds like your driveshaft has been thrown out of balance.  It would be in your best interest to have the shaft rebalanced.  An out of balance driveshaft can damage the rear end or transmission and can be just plain annoying to drive around with.  
Hope this helps.