My 1999 K2500 GMC 6.5 diesel Suburban has been having weird issues that are getting worse (310k, auto).  The initial symptoms felt like the 4wd is stuck on.  Tires are getting ate up, and when turning the wheel hard while backing into a parking spot, it feels like a wheel is stuck or turning at a different speed.  (A lot of binding/shuttering, sometimes so bad I can't back up)  There's been a loud "ping" noise on occasion when driving forward, and now whenever I release the brake pedal from a stand still, there's a shifting or sticking feeling.  I thought my brakes were sticking, but it's been getting worse, to include some binding and something just not right doing a minor forward turn. It originally seemed to be the rear wheels, but lately seems like both axles are having issues.  I've had my rear differential and 4wd actuator checked, wheel bearings and rear drum brakes redone, and replaced almost every suspension component, but nothing seem to help.  I'm moving across the U.S. soon and I don't trust it to make the journey.  Any help would be greatly appreciated!