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