I have a new hydraulic control replacement valve and it is different from the old one I just removed. (Which has a long rod on the end of it). Will the new one they just sent me work? And what is the purpose of the long rod and square piece on the end of it?
The square piece and rod are part of the oscillator. The square piece fits in a cam on the pump crankshaft that reciprocates. This causes the valve to rotate back and forth to keep the valve from sticking. The valve occasionally sticks on earlier models so the oscillator was added to the TO-30 and late production TEA-20 models. As I recall, the replacement valves are notched to accept the oscillator. You should be able to remove the snap ring in the valve, install the oscillator from your old valve and reinstall the snap ring.