hi i have a fisher v plow on my 02 2500 chev, the right side wing will not move allthe time and when it does it makes a sound like the motor is working to hard. allso when i put the plow on "float" in doesnt let me push the ram down also when its going down the motor makes a sound almost like the fluid is going backwards. can this be caused because of old fluid. i was thinking that it was the a valve. if it was how can i check it and replace it