Yes, it is a gear tranny. Yes, it has unfortunately sat outside. The clutch works fine for traveling in any gear but just will not let me engage the PTO shaft. The PTO has not been used for about two years and it did work fine then. The other day, after motor had warmed and it would crank promptly, I timed it just right once so as to engage PTO as motor fired. Then mowed about an hour with many start and stops. Then when finished I restarted motor but it still would not let me engage PTO without the severe grinding so I did not and will not force it anymore. I there a separate adjustment for the PTO clutch or a way to get it unfreeze from the flywheel if that is the problem?