Tractor Repair: Hydraulic System IH 674, filter canister, drive assemblies

Question
I just finished draining and cleaning the system. I broke down both final drive assemblies, cleaned and inspected the brakes. I've put every thing back together. I put about 9 gallons of hydraulic fluid back in, and it doesn't seem to be pumping the fluid. Does the system need to be primed?

Answer
  I will assume that you also changed the filter if you did all the other work.  There is nothing to prime, it should start pumping by itself.  Check the filter canister to make sure it is seated properly in the groove that it fits into.  Sometimes the bolt is tightened and the canister is not seated properly which will cause the pump to suck air.