Tractor Repair: 1980 international harvester 464, international harvester, rear blade

Question
Big Dean.  I have a 1980 international harvester 464 tractor with a 3 cylinder diesel. the problemexperienced is the hydraulics for the rear blade will not operate unless the steering is turned to a full lock position (rt or left) the fluid level is full and power steering is otherwise normal. any suggestion as to what may be the cause will be appreciated.

Answer
Hi Joe
  I am not familiar with the IH 456 steering but it sounds like you have a priority valve sticking. On tractors that use the same pump for the steering as the one used for the three point they have to have a priority valve the steering on those have priority over everything else. Hope this might help some Big Dean