The tranny will take more than it's rated for. The differential is pretty stout with 31 spline axles. I would say anything over 500-525rwhp you could be asking for trouble. Mine is at 490rwhp (mustang dyno) and it's had some seriously hard launches with Mickey ET Streets at about 4800 rpm's at the track. Haven't had any problems or noises to speak of. I've had the tranny out a few times and have not had the input shaft twist at all. One thing to note is the stock clutch is a total POS! Also, don't believe the stories about how weak the motor mounts are. Haven't had a failure yet.