Lack of drive to one side only cannot be anything in the hydrostatic transmission -- it has to be in the final drive.

There's a link below to the "master thread" where these problems are discussed, mostly with respect to wheeled machines. At the bottom of the thread there's a post with a link to a website with exploded views of the whole machine. With a little probing, you can find your machine on there -- I'm looking at it now.

It appears to me that on the tracked machines there are similar pins on both ends. Unlike my wheely (and possibly depending on serial number), these pins look like they're designed for replacement. Look at Item 14 (at least on the particular drawing I'm looking at) on the "Right Transmission Case" page. I'd start there.

Post when you've got it figured out, OK? Good luck.

Here is a link that might be useful: Honda snowblower drive problem thread