This isn't like the bigger model Clarks that have a steerbox and the valve is bolted right to the steer cylinder. It uses the same cylinder but without a valve. Instead of a steering gear box it has a modern type Orbitrol valve that's connected to the steering wheel. The Orbitrol just sends pressure down to the cylinder via hoses.

Anyway, I got a rebuilt cylinder from Hader. They cut the welded cylinders apart and rebuild, then weld it back together.

I would think the piston seal is like a steel piston ring like in a engine.

Put it in today and all is well. I've never seen one of these Clark type cylinders have a problem like this before (drifting and wheels not reacting to turning the steering wheel).

I proved it was in the cylinder by removing one of the hoses and plugging it. Then capped off the cylinder fitting. Started it up and tried to turn the steering wheel and I couldn't.