yeah, I havent really heard of anyone breaking a retainer either. Anything can be broken tho, i suppose. Looking at my HAD flange setup, and the thickness of those retainers, I'm not sure I'd run em on my t-case. There is VERY little extra room to work with between the HAD flange and the t-case stuff to get the bolts that hold the driveshaft on. How much thicker is that retainer than the stock one... or is it the same thickness and I'm just smokin crack? lol!
j