I have a Lawn Boy Gold Series . Model #10515 S.N. 3913965 I would first like to know how old it is. I bought it new, but it's been a while. I don't remember when. It is self propelled, rear wheel drive. The problem is this. When you release the lever and try to pull it backwards, the transmission is still somewhat engaged. Not enough to pull it forward, but enough to make it very hard to pull backward. I have checked the belt when the lever is released, and it is loose. What am I overlooking? I can't say for sure if the belt has ever been replaced, but I have always had it professionally serviced. I am retired now, and thought I might try to tackle this problem myself. Maybe that was a mistake.