thats not un common for these trucks though, check your inner pads if your outers look ok, i just did a maint 2 on a guys f150 and found his rear inner pads to be in the red but the outer was still green

 

Dammit...I rolled down my windows, put it in reverse, and hear a distinct clunck when I back up. Goes away after that, and only in reverse. I'm a mechanic, so I'll figure it out when I get a chance, but has anybody had that happen yet? Driveshaft has no play, so the gear mesh/preload is good fore and aft. If I get a chance, I'll grab a lift this evening, pull the rear wheels yank the rotor/drum combo and check the park brake, but for some reason, I don't think that's the culprit.