Europa

Okay I've taken the snowblower and stuck a mirror underneath and I can say with total confidence the drive plates aren't contacting - it's 100% vibration rocking the snowblower backwards. I also think I know why it suddenly started doing it. When I did my full maintenance I also lubed and greased the two chains that actually turn the wheels. In doing so I think I eliminated any friction that was there. Essentially, it's so lubed up the vibration is now enough to move the wheels. Oh well, at least I know for sure.

No, no. No offense taken. But you've hit the nail on the head. How can it go backwards if the it's in a forward gear? How can it move at all if there's clearance? I'm going to try and have another look today and see if I can see what's happening. The worst thing is that I've posted in several other forums and there's a lot of people with their snowblowers doing the exact same thing. Weird.

Borat, what you say makes sense - but it isn't the case. The gap is well within spec and I've checked the actual clearances myself and their fine. Also, it goes in reverse at idle while it's in any gear, I could have it in top gear and it sill goes reverse - there's no way there could be contact on the reverse section of the wheel. So it still doesn't explain it.

Yeah mine goes backwards with a certain degree of force, but if the plates aren't engaging how the hell can it happen? I might tip it on the bucket with the bottom plates off and actually see if I can see what's happening.

I just don't like the idea of the snowblower being able to move on it's own. I'm sure that once the snow is down it won't actually be able to move on it's own, but still I'd correct it if I could.