Rusto

Greetings, I have a 1999 Jeep Grand Cherokee Laredo 4x4. Automatic. I have recently noticed a sort of rumble coming from the vehicle (maybe the rear end?, hard to tell). I is most pronounced when I accelerate....in any gear and it occurrs when I brake....even when I brake while the transmission is in neutral. I had two incidents that occured within the week before I started noticing the vibration/rumble: 1. I side swiped a curb (right side of the vehicle) while driving 35 MPH. Appeared to scuff up the tires, thats all. This may be the more important one, I was coming up to a sharp fast turn and I had to brake hard so I decided to put the transmission into 2nd then 1st while hitting the brakes heading into the sharp right 90degree turn. Dont ask me why I did it, I thought I was in some sports car I guess. Anyway, I am confused as to why is happens when accelerating and braking. Any help would be appreciated.