Haywood SP-710 Control Valve chatter

We've had our pool in operation for 5 years now. Everything; pump, filter amd valves work as they should, but ever since the pool was installed there is a constant loud chatter that comes from the filter control valve.

I thought that this was normal until I helped a friend get his pool opened for the season. When his pump/filter system is running, all you hear is the hum of the pump motor. When my system is running, you can't hardly hear the pump motor for all of the noise coming from the control valve.

Tonight, just out of wonder, while the pump was running, I pushed down on the valve handle. The chatter stopped completely, but while the pump was circulating water in the pool, it was also discharging some water out of the drain line.

Anyone have an idea of what may be causing this chatter in my valve?

Usually that noise is trapped air around the valve ports that isn't being flushed out. Pressing down on the handle while the pump is running can damage the spider gasket. If it isn't glued in the channels one or more of the spokes can lift out and when the handle is released it will be crushed and deformed. This explains the water out the waste line. Usually that chatter noise will go away in a little while. Mine does it periodically but shuts up after 15 minutes or so depending on how much air I got in the assembly. If the pump isn't ramming enough water through the thing the air may never be purged. Hope this gives you an idea what to look for.
Al