Shaking

We have a 1996 Jeep Grand Cherokee Limited, V-8, 4WD with 188k miles. We have the same problem that is described by the owner of the 1999 Jeep Grand Cherokee Laredo. That is, the vechicle will shake violently when it hits a bump in the road. This seems to occur randomly and at speeds above 40 mph. When it happens, the whole front shakes up and down as if I were driving over a rough road. The shake is at a relativitly high frequency of at least 2 per second.

I have taken it in to the shop and, of course, when they test drove it nothing happened. They did put it on a lift and checked thightness, etc. And even ran it to make sur drive shaft and U joints were aligned.

Your response to the 1999 owner was to check alignment. If alignment were the problem, wouldn't this show in unusual wear of the tires such as the tread not wearing uniformly from inside to outside? What would recommend to change first?

Thanks much for your help.