I have a 2002 Astro LT 4.3L rwd, and after changing the steering gear box it makes a hissing sound from the steering wheel through the steering colum. It sounds like the power steering fluid that is being pumped through the steering gear box. I have replaced the power steering gear twice and it still makes the hiss noise. Also, flushed the system and replaced with GM PS fluid and also tried a synthetic fluid. No change. The sound occurs when the wheel is turned in either direction at idle or while moving. I have read similar threads about this type of noise with other GM trucks but can't seam to find a solution.
Thank you for any possible suggestions.