Tractor Repair: International 300 Utility Tractor, several thousand dollars, utility tractor

Question
It did't quit, but was not working correctly.  It would go up and down very slow and shake.
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Followup To

Question -
We have a International 300 Utility tractor that has just been repaired to include new hydrylic pump & valve body.  The hydrylics now work fine, but the tractor still makes a terrible whine.  My husband was going to replace the water pump, but realized after disconnecting the pump, the tractor still makes the whine.  

Any suggestions of what it may be?  We now have several thousand dollars into this tractor and still not right!

Answer -
Did you replace the Hyd pump in an effort to cure the whine or did the pump quit?  

Answer
The best direction I can give you is to elminate all the other items that run off the front drive -- alternator - fan --- If all other items are eliminated -- it can only be the new hyd pump or the timing chain / belt on the engine --

Bleed the hyd system just to eliminate the possibility of air in the system.