I've had this odd issue with my Jimmy for some time now. It seems to have recently gotten worse. The symptom is that if you floor it from a stand still it sounds almost like a tire rub sound on the front right. Like a rumble...but it isn't a tire rub. It's recently started making the same sort of sound when I'm sitting still. If I place the vehicle in N or P, it goes away. If I rev the engine in P or N...doesn't do it. If I power brake it will do it, again sound comes from the front left tire area sounding like a tire rub. So that rules out brakes, etc. The ONLY thing my limited research has found is MAYBE my 4x4 isn't disengaging fully? Suggestions

 

Not sure on that one. Sounds like something is loose and vibrating under certain conditions maybe? Is it both the right and left side, cause you said "right side" in the 1st part of your post and "left side" later in your post. I remember when my catalytic converter went out, it rattled under certain conditions. I found out it was the catalytic converter by simply reaching under the car and banging the converter with my hand, at which time it would rattle like a jar of marbles. Of course you say the sound comes from the front so that wouldn't be the converter.

 

Well...it appears I have 2 issues. One I figured out this morning. I had installed a new catalytic converter a couple of weeks ago. The rear pipe is vibrating on top of a brace on the underside of my truck. So that's the vibrating noise. I just need to get under there and readjust so it isn't hitting the brace.

I still have the rumble noise on the front right though. It only happens when I get on it...like floor it. I think it might be that hub partially stuck in 4x4 because it's the only thing that makes sense. I've had the drive shaft replaced and that didn't fix the issue.

 

Just guessing here. I'd look for a bad motor mount and check for a worn front axle CV joint.

 

Sounds like a bad motor mount. Drivers side of engine lifts when power braking.