Grand Cherokee vibration

When I have my jeep in drive and at a stop sign it vibrates violently, the same thing happens when I exceed 55mph, any thoughts, otherwise it runs well just can't seem to find a mechanic to figure this one out.
Thanks

I have a similar problem. I am not sure this will help you now. The front axle shakes violently when the wheel hits a bump or pothole at a precise angle and I have to slow the car down until it stops. At first it seemed to be that way, then the problem only got worse. After putting it off we had to replace the front axle, have it aligned, replace the brake pads and rotors. We paid over $750 about 4 months ago and the problem just started up again. I would be very interested to hear how you solved the problem. One mechanic said something about a worn bolt that is hard to access and quoted over $600 to repair.

What forsaken has described is called "death wobble." I is caused by unbalaced tires, bad cv joints in steering, a bad steering stabalizer (or not a large enough one if you are running bigger tires), if more than 33" tires you need a drop pitman arm, loose bolts in control arms or trac bar (if you are lifted more than 4.5ish" and haven't upgraded the front trac bar then that "could" be it). So start with an alignment and tire balacing (have them check the bolts on the control arms and trac bar and weather or not the cv joints are bad.

malaokah, you are not describing death wobble at all, you probem (since it excists at a stop) can only be linked to the engine or torque converter, could be engine mounts (doubt it but check then anyways), need more info on what it is doing specificaly (high frequency ect...)

i have a 94 grand with death wobble and just found out my motor mount is broke in half getting it fixed i hope this is my death wobble