Suburban :: Low Grumble Sound When In Motion

Just new today a low grumble when in motion. Not the engine, all gauges check. This sound, it's constant unless I am at a complete stop, a lower sound than the engine running. There has been a putter sound for a while now, was told that was an exhaust leak. That sound I thought sounded like the bolts on the front fan hitting something, cuz that happened before, but so mechanic said it was an exhaust leak. That a very faint putter sound. So what have I got left? Something front end, I have a tiny clunk when breaking and taking off. It doesn't seem to be related to the usual stuff I've already had happen. Breaks are fine, tires wearing evenly, engine doesn't skip a beat, temp good, isn't the sound of low steering fluid cuz I know that one.

Could where ever an exhaust leak be finally break loose? I know diesel mechanics but who looks at the wheels and shocks and stuff? Just sounds like something in addition to the engine, not tire on pavement hum but something lower. Sort of surrounds you, windows up it is very faint. Doesn't affect anything either, that I can tell. Muffler? I do have a vibration noise on and off with the muffler. The best I can describe it is a low constant noise while I'm driving and it's there going slow and fast. More audible with the windows open. All I know is I don't wanna die in that truck. Been under it before and other than old leak stains, all I've ever seen is dirt in my eye. What kinda shop does shocks and wheel stuff? What can an exhaust leak do to me? Not even a vibration to go with this noise. I just don't know, this is new.