back wheels wont turn

well my hardbody is bagged out and it was sitting for a couples of months now.I decided to turn it on today and take it for a spin around the block and the back diferential locked. I dont know what the problem is. I lifted the wheels and they turn and i checked to see if it had oil and it does. I can only think of the drive shaft being bent or just f**ked up HELP ME OUT HERE ANYONE