Did replacing the bolt fix your problem? If not start with the basics, What trans do you have? Auto ot STD? A bad Torque convertor can cause this. Also, start with the simple thing and move up. Check you Trans mount, on the TJ they have a habit of tearing. Move through your Dshaft and if the Joints have never been done, chances are they need to be. So do those. It doe not sound like you are having Death Wobble. But run through your Tie rods ends anyway and have someone steer back and forth in the Jeep while you watch your front end. Look for play in the Track Bar and Tie Rod Ends.
U-joints failing can cause quite a bit of damage, you have them on the front, rear, and in the front axle. If your Jeep is close to or over 100k miles and they have not been done, do them all. One of the Cheapest things you can do to maintain the vehicle and will last another 50k miles or so.
There is also a possibility that you have a bearing out on the rearend. This will cause a vibration when under loads like excellaration. This is way more detailed fix so I would start simple and maintance the stuff good till get to the problem. I find that most of the Jeeps driveline problems that I work on or due to abuse and maintance.
