Hi, Had a loud clunk while driving down the highway in my 1993 GMC Sierra in 2wd, and lost all drive. Can still feel the tranny shifting in and out of gear, but there's no drive to the wheels - except in 4L, which seems to work fine (albeit with some whirring!) I'm suspecting transfer case, can anyone confirm this before I pull it? Linkage seems to be fine with a positive shift, although it does sometimes take some grinding and effort to get it into 4H and 2H. No visual signs of leaking fluid. Thanks in advance!