The rack and pinion assembly in these trucks is prone to significant leaks and failure at higher mileage. The leaks are subtle and often will not make it to the ground, my power steering fluid loss from the reservoir was about 1 quart per year. Major signs of this issue are sloppy/lazy steering, significant bump steer on rough roads, a loud power steering pump, and difficulty steering at freezing cold temperatures before the car has warmed up to operating temp. Unfortunately, these are also signs of a bad power steering pump/loose belt. The issue appears to be seals in the rack are leaking, therefore causing lower fluid pressure.

The only full resolution from Toyota/Lexus is to replace the entire rack and pinion assembly with another unit that may eventually suffer from the same problem. Trying to rebuild the seals is almost impossible in these units. The issue is not cheap to fix but can be lived with if fluid loss is minor and you are aware of the changes in steering, however, the possibility of a failure while driving and loss of power steering is possible. A small amount of thickening agent (Power steering leak stop at your local auto parts) added to the fluid can reduce leaking if the seals have not failed yet.

Also, the rubber return hose going into the power steering reservoir is notorious for seeping fluid all over the serpentine belts, making a noisy mess. The hose and its clamps are an easy fix.