M MINGLE Pressure Washer Undercarriage Cleaner, Under Car Wash, with 45 Degree Angled WandNew pads and rotors this week; hoping it is good for another 40,000 miles (salt willing).
Plug the above into an Amazon search window and check this out. I use it to clean under the RAM because I live in the salt belt of Maryland. It worked nicely for me. I'm assuming you have a pressure washer but if not, don't skimp on buying a nice one with a significant psi rating. There are other versions of the undercarriage washer on Amazon if you don't like that one.