On our Duramax Diesels the power steering/ hydro boost system needs to be flushed approx every 50k miles. In these high heat systems the P/S fluid breaks down fast from normal use. If your towing it breaks down even faster because the P/S system feeds both the power steering system and the brake systems hydro boost unit. Large tires, heavy loads, off-roading, towing all contribute to the loss of viscosity in the power steering fluid due to high heat in the fluid from these conditions. The Duramax systems do not like the use of standard automatic transmission fluid like your fathers car did years ago. That is why we here at MadJack Diesel Performance have put together a complete kit with the best synthetic power steering fluid available on the market for you to do your flush and get your brakes and power steering back to the brand new factory feel. This is one of the easiest maintenance processes to perform even if you are not a mechanic. Ask us for a link to a write up on one of the forums to explain the process.