My pre-owned 2001 CRAFTSMAN Tractor Model 272430 is having difficulty shifting gears. It seems that the clutch is not disengaging completely. When it is fully depressed and I shift into gear, the tractor lunges slightly. Then I have a tough time getting the shifter to move back to neutral or any other gear. However, when the engine is not running, the shifter moves freely. Is there an adjustment that can be made somewhere? I do not have an owners manual. Any diagrams would be helpful. Thanks.