Ariens 824 snowblower drive

I fixed up an older Ariens 824 snowblower and got some use of it till this week, when it wouldn't move in any gear. After fiddling with the lever and such, it started working, but now again when it's cold it doesn't want to move.
It has a new v-belt on it. I checked it and it's fine. I turned it over and removed the bottom cover. The friction disc and drive wheel look fine and engage properly when I hold the handle lever in. It found that I can hold the differential/spur gear and move the shaft/wheels.....the spur gear stays still. Is there a key or pin that might have sheared? I don't want to diassemble everything and found I missed something simple.
Thanks,
Bill

Hi - did you get this figured out? I have a Ariens 524 with similar situation. Thanks

Hello Mark,
I asked this same question on a very helpful small engine site. I'm pasting a link to the thread below. If the link doesn't open, then copy and paste both lines of the link info(from http through the number 2538) into your browser, should work. Hope it helps!
Bill

http://www.perr.com/phpBB3/viewtopic.php?f=14&t=363& p=2538&hilit=ariens+824#p2538