the syncros on second gear seem to not really like downshifting into second at all. I find double clutching helps, but don't downshift into second with a closed throttle, i think that's when they break.

Gearbox strength is not measured in horsepower, which is a measure of work. Instead they are rated by torque, which is a measure of twisting force.

The 5-Speed tech section article lists the approximate strength of each gearbox: 56, 60, and 63 series. It doesn't matter generally if it is a 4-speed or 5-speed.

ohk, thanks guys. will prob get a 60 4 speed if the 60 5speed never comes up.