I recently bought a 91 f350 diesel with a 9' fisher (not minute mount) with a belt driven pump.when the fluid is hot the engine has to be raced quite a bit to raise the plow,also if the plow is raised and the control lever is held in the raise position at idle the plow will drop unless the engine is raced up. when the fluid is cold the plow seems to work fine in fact i can see the pressure line from the pump to the valve body flex with pressure when a cylinder bottoms out! any suggestions? also on the same truck i have found there to be a lot of play in the double ujoint assy. on the front drive shaft the joints seem fine it appears to be a bearing (or lack there of) of sorts between the two joints that is loose. would you advise me to replace or rebuild this. the truck has 150k mi.and an e4od auto trans. i have hade four trucks similar to this one and never these problems. thanks in advance!