what could it be and how to fix ??

i put my truck in reverse and hit the break to put it in drive but as soon as i hit the break it makes a grinding noise like somethins grindin, and sometimes i put it in reverse and here a popin sound. its a 4.3 automatic 4wd v6 vortec also my right blinker works when it wants too sometimes stays on and when u engage it it flickers really fast i have changed bulbs and checked fuses ?? any help much appreciated