nope that's all mud that's never been washed off, and it's a pita when you start working and it keeps falling into your eyes and ears!

 

So pressure wash the crap of the underside. Also one little trick for ya, get one of the lawn sprinklers that has the bar between two sides with holes in the bar. The bar swivels back and forth so put that under your rig and it will loosen up a lot of that mud and help clean it. You're asking for all kinds of rust and rot by not cleaning your truck plus you're hauling around 500lbs worth of mud.

 

I will when I get gas in it to go to the car wash I plan on cleaning the **** out if it, although everything is cleaned now because of my trans swap