I am having problems with my 2000 GMC Sierra Z71. First, it is having trouble coming in and out of 2wd. Since we went 4x4, it cant seem to stay in 2wd. Also, it has a ticking noise coming from underneath when the car is in motion forward and especially backward. We thought it was a bad chain in the transfer case and installed a complete new transfer case, but we are still having the 2wd/4wd problems and ticking.