Search the forums, I did a write up on fixing that about 3 years ago. Nevermind... here is the information
Pull the countershaft sprocket, slide the metal collar out and pop the little $6.00 seal out - might as well change it while you're in there. Look along the shaft and you will see a small o-ring. Slide it off the shaft and go to Home Depot and get one thats the same diameter, but it will be slightly thicker. Good news is it won't leak near as often and it's cheaper than a stock one.