My 782 hasn't had a deck on it for several years. Today I decided to put the deck back on to use. Worked to get the deck down out of the haymow and belt was still with it. The mule drive was never removed. Drove the tractor into the machine shed and went to lower the lift so I could get the deck on and the valve is froze up. Can't get it to move either way. Any ideas on how to fix this?