Buzzing Noise

1. Low fluid level.
2. Pump sucking air.
3. Valve body malfunction.
4. Overrunning clutch inner race damaged.
5. Governor valve; burrs, nicks, scores or binding on weights, shaft and valve. Collapsed or distorted springs or distorted snap ring. Cracked or warped body. Dirty filter.
6. Linkage improperly adjusted.