Jim,
My #267 is kinda like this as well, better on snow but once in a while in snow as well it fails to resopond, or as I unwind the wheel it suddenly starts turning....Also notice some times when it gets stubborn turning left, if I lift out of the throttle it turns around. But most of the time it turns left just fine, especially on snow. I have checked every thing except the tensioning cells that are set at the factory, with center punchs to lock them. (the ones the manual says not to tension the belt with) I am unable to see that the nested coil springs in the cells are broken, but the bottom set are hard to see while in the machine. We performed Lyndon's procedure for centering the variator relative to the center of the steering box as well. So I am like you, wondering if belt slip is causing this? or perhaps I over greased the variator shaft and contaminated a sheeve with grease? You would think it would be spead by the belt, and muck it all up, if grease was doing it. One other possibility is that our belts are just thin enough in width, to bottom out and ride on the nonload bearing inner face of the belt, causing it to slip, on one side but not the other... Before we adjust the belt tension and centered the steering box/variator it was, I would say, definatly bottoming out on one side of the variator sheeves. So adjusting helped, but didn't eliminate the issue. But it only happens occasionally on mine now. Don't know if it means anything but if you let go of the steering wheel it very slowly drifts slightly to the left. I am thinking this might be an issue with track lengths of each track however....but I am new to the Snow Trac as well....
So I will be watching this thread......
Best regards, Kirk