I've put all 4 of my 939's in reverse while in low range MANY times. I didnt abuse the trucks while doing it. Ive backed a loaded dump trailer (80,000 lbs) up a(very tight ,very technical) slope, stopping and starting. I've backed my m932 shorty up a 25 ft high embankment so steep it lost traction and dug in. I think the key to breaking the t-case is all in your right foot. Get a loaded truck stuck and try to power out in reverse and your gonna have a problem - put it in reverse with the engine revved up and your gonna have a problem.... you dont want to shock it at all. Be smooth and you'll be fine.