I have a stx 38 j.d. yellow mower, when i put it away the tractor would not go up hills (had to shift to lower gear) and was getting worse. would putting on a new drive belt solve the problem or is there a adjustment on the clutch part to tighten things up as i will have to get it out and pull the mower off to get up in there to see what is happening. How does the clutch work on this model to tighten the belt. My old 67 110 works on pulleys to tighten the belt but not sure how this one works. thanks for any help