I purchased a M4500DT. The PTO clutch control lever won't disengage the PTO gears to allow me to move the Ground PTO gear shift lever. When I try to move the Ground PTO gear shift lever, I just get grinding gears. If I shut the tractor down, I can then shift the PTO into gear, but I can not disengage the PTO using the PTO clutch control lever, so I have to shut the tractor down to shift the PTO out of gear. Am I doing something wrong or is there a clutch problem? Thanks to anyone who responds. Dennis