as r31nismoid said, these gearboxes are about as tough as any going around. that said, any gearbox will eventually break from constant 6k launches...may want to revise your driving style. also, when buying a second hand box, and go and get it rebuilt properly or at least checked out. a box that has been broken then rebuilt is better than a second hand box as you won't know the condition its in. not sure how you lost 1st and 5th gears, but it sounds like you have stirpped 3rd gear. i'm also assuming you still have reverse?