Need some help with my case 970.....pto started slipping under load then quit altogether. So I pulled the pto clutches and had case dealer rebuild it, put it back together and that didn't cure it. pto shaft turns when engaged but I can stop it by hand. Clutch plates were worn and curved/blue from overheating so I was sure we had it. now thinking maybe its in the hyd vavle where the pto cable goes into, does anyone here know what the pressure is supposed to be?