My 6 year old, 17 hp craftsman lawn tractor is having problem with power. On even the slightest slope, there is not enough power to go uphill at normal cutting speed. I need to downshift, and go very slow (trade speed for power). The drive belt looks OK, and I don't see how to make any adjustments to tighten things up. I'm OK with replacing the drive belt if necessary, but I suspect that it's not necessary...

Is a hydrostatic drive transmission...