Originally posted by TampaWRX
The STi 6-speed is much tougher than the WRX 5. It has a more rigid case, which helps with alignment, beffier gears, better oiling, etc. It is a vast improvement and I have heard of daily driven, 400whp cars running the factory trans for thousands of miles and counting. It is a very robust upgrade, but very expensive as well.
its funny you say that...cause i have a friend who just put an STI together...made like 375whp...and it just destroyed the transmission.
obviously some drivers are harder on transmissions...but i still wouldn't take any chances and keep the car around stock horsepower levels.