01 gmc sierra c3 awd (the first denali)
 

I found that after driving for 25 minutes or longer periods my truck develops a heavy clunk along with my rear wheels dragging when turning it feels so bad i picture things snapping underneath but after I leave the truck to cool runs fine until fully heated again I rarely experience the clunk becouse my drive to work is only 10 minutes again any further and it's happening at every corner I love this truck and would like to keep it any ideas please help