2002 Zr2

Hello

I have an '02 ZR2 4WD 4.3L, I have had an intermittent and unpredictable "thump" that comes from the front end when stopping and the front end flexes down. I can feel it through the floor boards when it does occur. I have had the U-joints and ball joints inspected twice which have been reported back as fine. Recently, I have noticed a grinding noise from the front end when I turn sharply to the left and accelerate. Any theories?

Thanks in advance for any assistance.

I have a 99 2wd S-10 that feels like it is doing the same thing. When I jack up one of the front wheels, should the Idler arm have any verticle play? When I try to move the jacked up wheel from side to side, there is a fair amount of play.