Hello, I've never used a forum to find answers before but I haven't had any luck finding someone who can help. I have a JD STX38 black deck hydro. It recently threw the belt while mowing. It looked pretty chewed so I figured it's probably old so I bought a new belt for it. I put the new belt on and it won't stay on for more than 10 seconds. I've checked the pulleys on the deck and everything looks good besides the tensioner moves up and down(the whole arm). Is it supposed to? I've tried tightening it but it won't remedy it's movement. Anyone know anything on this? Any help would be greatly appreciated!