okay so basically whenever i put my truck in to reverse it clunks and kinda jumps a little bit i know this is not good at all what is wrong

 

Check the drive shaft U- Joints. They are probably shot.

 

mine does the same exact thing. before i knew what the problem was i thought it might have been the u joints. but when i opened my rear diff i discovered the gears worn to ****. they had so much play in them. so you might want to check your u joints and if they seem fine check your gears.

 

alright ill check both i dont think its my drive shaft u joints i just looked at them the other day but not closely so i will double check that then check the gears thanks guys