Im working on my brothers NV5600 6-speed. He has a 2003 3500 4x4 SRW cummins with about 550 rwhp. he broke 3 gears (5th cs, 6th ms, 6th cs) while racing a megacab. he was in 2wd (Cause of a bad front axle u joint) and on dirt when he did this. missed his shift from 2nd to 3rd. so the question is should i just replace the gears and put the trans back together? or does he need some kind of harder gears? i have heard a little about cyro treatment, is this something he should do? it is just a dd/ play toy. thanks for any input on this topic. Jason