Mark made some good points. If it's noisier with the brake on, neutral needs adjusted. If not, it's air being pulled in from a low pressure side leak or cavitation.
ALL hydraulics make some noise. I'd rather have a noisy one than one makes no noise.
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Travis
1993 Cub Cadet 2064
1988 Cub Cadet 2072
1980 IH Cub Cadet 782 w/CH20
1966 IH Cub Cadet 102 w/K301
1961 IH Cub Cadet O
1967 IH Cub Cadet 102 & 122
JD 2155 w/ 175 loader