I HAVE A 1986 843 BOBCAT THE HYRDAULIC MAKING A WHINING NOISE AT LOWER ENGINE SPEED AT FASTER SPEED NOT AS NOTICABLE, I HAVE CHANGE THE FILTER AND FLUIDS TWICE, THE HYRADULIC PUMP CRACKED ON ME, NEW PUMP INSTALLED STILL HAVE WHINING NOISE, USING ORIGINAL BOBCAT FLUID, MACHINE RUNS FINE...