420 steering clutch blues

[maplebones]

I've had a 420c with winch and blade for about 7 years. It's not real pretty and it's been around the block a few times, but it's done a lot of work for me around the farm.

I don't usually strain it very much, but this spring the snow was rediculous in the maple sugar bush and it was quite a chore to open up the roads. After a couple of hours of working her hard the left track most of it's power. I was hoping it might be better once it cooled down. The next morning I was back at it, and it seemed to be working normally until today when it repeated itself after hauling some pretty big pine logs uphill.

It's cooled off now but it doesn't seem any better. Looking at the clutch on that side, there's about half the adjustment left on the throwout bearing. There's no evidence of oil or water, it's clean and dry, and the fingers on the clutch are moving freely. I know I'm probably looking at a rebuild, but the thing I don't understand is why it's so weak in all forward gears yet seems to be fine in reverse. I hooked the blade behind a tree and backed up while releasing the right steering clutch and the left track spun like there was no tomorrow on pretty rugged ground. That seems to me like full power. I'm wondering if there's something else going on .