Have a clean, low mileage, (120000), Chevy 2500hd. I use it to tow my fifth wheel. I recently had the power steering lines leaking, so did a complete replacement including return lines. I flushed and filled with Royal Purple synthetic power steering fluid. Almost immediately after completing the job, my pump started making noise. First it was just a soft hum, then while turning, and/or braking it would growl. It gradually would make at least some noise all of the time. I must admit that I had not been replacing the fluid as I should have. I went ahead and replaced the pump. I again flushed and filled with Royal Purple. The pump runs quiet now, except under hard braking with the fifth wheel hooked up. There is no noise while steering. Everything is quiet when the truck is not loaded. Heat also may be an issue. The pump will stay quiet until the fluid gets hot. I have read about power steering coolers, but the truck is not equipped with one. I am interested in speculation as to my use of Royal Purple, and also the possibility of retro-fitting a power steering cooler. It seems GM has discontinued the OEM units for that vintage. I know Dorman makes some. Also what other issues might I be missing. Hydro-boost is original, as is the steering gear box. I'm running stock tires, and no lift kit. What do you think?