I'll take a guess. Viscosity of fluids thickens as temperature decreases.
That thick fluid has to travel through restricted orifices in the engine/trans/powersteering. As fluid is pumped through these areas, it is forced to speed up, pressure builds and aeration occurs. The whine is from the aeration.
A mechanical engineer might explain it better.
That thick fluid has to travel through restricted orifices in the engine/trans/powersteering. As fluid is pumped through these areas, it is forced to speed up, pressure builds and aeration occurs. The whine is from the aeration.
A mechanical engineer might explain it better.