Rep Power: 258

I was on my way back from Houston with some friends. A little bit outside of Houston, my car starts getting really shaky, like I've just hit some of those stay awake treads on the side of the road. It keeps doing this for the next 2 miles. I have to tap my brakes while im on the road, and my car starts making a popping noise, like a flat tire makes. I assume I just have a flat tire. I pull over, and nothing seems to be wrong. I drove back the rest of the way, and noticed that when I hit the brake, or decelerate in any way, it starts making this popping noise, along with a slight grinding noise. I can't figure out what it is, but it's very loud, sounds like it's coming from directly under the car. Have a feeling it might be the tranny, but I dunno. Could be an axle maybe? Any input would be awesome.

I really need any opinions on this.

bump