Making a roaring sound when started and when gas is pushed?

About 4 days my wife told me our car was making a roaring sound that she had never heard before. I listened and could barely tell a slight difference. Today I started the vehicle and it was much worse. The sound is barely noticeable from the outside, but in the interior it sounds like a loud roar almost as if it has an exhaust leak. It seems to originate from the front passenger floorboard. You can feel it in the key upon startup, and while idling in park, there is a slight vibration in the steering wheel. After inspecting the exhaust system, i've found no leaks. Tha cat conv are good. No check engine light has come on. I changed plugs. The only thing wrong that i've sen is the tran fluid was low, and while inspecting exhaust, I see that one of the lines from the tran [i assume it runs to rad for cooling purposes] has a leak. Please help. My family and I are supposwd to be pulling our popup out of town this weekend with this car and go camping. Almost forgot to menrion that there seems to be a slight loss of power.