We have a Massey 85 tractor that won't keep hydrualic pressure on the PTO clutch. The clutch pressure and steering run off a small Cessna, (seperate from the hydrauliuc system). I get 4gpm and 25 psi @ 750 rpm. At 2100 rpm 4gpm and 225 psi. The PRV dumps @600 psi. Our shop man. does not give us...