I searched and searched the web for all the wrong things. My mower was running fine, then I heard a gentle "clunk" noise and suddenly my lt2000 wouldn't stop its forward motion (except by way of the tree I was trimming around). I put it in reverse to back away from the tree and then it wouldn't stop it's reverse motion. After searching the web for which part of the clutch I must have broken, I stumbled upon this site. Then I figured it out. The rear drive shaft (located below the seat) engages when the belt is firmly seated inside the pulley woth full tension. Without tension, the belt loosely circulates around the pulley and there is no drive action initiated. When the belt goes bad, it stays engaged on the pulley and keeps the mower in drive. It can also happen if the tensioner pulley or spring goes bad. So if your mower won't disengage from a drive motion when you have the brake/"clutch" pedal depressed, it most certainly has something to do with your drive belt or tensioner pulley.