reverse

I have a 99 Tahoe LS with a 5.7L 4x4 4l60 trans. I start vehicle. Put trans in reverse. At rolling speed after about a foot or two I hear a clunk and feel it in the front end. It drives fine after that initial clunk. Does not happen when starting from a stop while driving. Brake pads...

Changed fluids on gf's 2002 4wd Tahoe LT 5.3L, changed front and rear diff, dropped tranny pan and flushed(looked "ok", no large shavings), put new ACDelco filter, flushed transfer case (was almost dry/old oil was super black, also like 2 small (7mmX7mm?) pieces of white plastic came out when I...