When I worked as a wrench for Dodge, we sometimes would get different type of feedback noises off pressure hoses, whether it was A/C or P/S. The fix from Ma Chrysler was to put a 2-piece counter weight on the hose to change the dynamics. Maybe you can try a weight like the ones they have for kitchen faucet hoses that pull the hose back into place? Bolt it around the P/S pressure hose. Worth a try to unbolt from the sink to try it out, eh?
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That's a good idea and very easy to try. The same concept could work if the harmonic is exciting a resonant frequency in the steering column by clamping a weight on the steering shaft. Works like a resonator in an exhaust system does to change the natural harmonic frequency of the system.
