With cooling our boxes can take over 400 HP for long periods. I had one last three full seasons and when pulled apart only needed the LSD clutches worked on, the rest was fine. That being said it was NOT just a turbo gear driven cooler, it was a tilton pump with a spray bar at the R&P mesh and there were two filters inline as well. By the way that car had lots of aero work and 335 slicks on it!
I have had 1000 HP go through a 951S box on the dyno and then 800 HP on the track but that box was never intended to go more than a few weekends before freshening. Never broke that one either, but did change bearings often as well as fluid every weekend.
I think our boxes are well made minus the cooling issues and lack of directed oil lubrication/cooling where it is needed.
That all being said a driver can break a box or keep a box alive just the same. I have raced a lot of 901 gearbox cars too and NEVER broke one of those which is saying something. On the other hand I broke Getrag gearboxes in my BMW race car left and right and those are supposed to be tough, go figure!
