I have a1996 V-8 Grand Cherokee.
On occassions when I hit a bump ormake a turn my Jeep starts to shake violently like an earthquake forma feww moments then stops...any suggestions?  

something is worn out in the front end. there are all sort of links there and you GC is 10 years old  

Start with the basics, like look under and give it a lookie loo and see how it all looks and see if some thing looks outta place. Second thing is to jack it up (if you find nothing wrong visually) and then pull/push each tire and check out your  joints. Also turn the tires back and forth while ya look at it and see what it does. also check your shocks and springs and rear end also. do a full visual and see if ya can find out what has gone wrong. Im suspecting it might have some thing to do with your steering. How many miles do you have on your ZJ?? Also be sure to check your steering stabilizer and see if its leakin any fluid at all. There could be a lotta things that are wrong or it could be some thing little and simple to fix. Good luck  

I just had the front aligned 2 days ago and Sears said everything was ok, but it still shakes like hell occassionally. What about a broken motor mount? What occurs when you have a broken one. Does it shake?  

I'd check the front end first, you have no idea how many joints and bushings there are up there waiting to wear out (I count 18 in my head, I'm sure I'm missing plenty of things). It could be an axle Ujoint or CV joint (with the front up, turn the wheel all the way to one side and rotate the tire by hand. is it smooth or does it try to bind?) I'd think the transfere case is a more likly culpret than the motor mount (get it up in the air, and try to pry up the transfere case to see what the mount looks like.) the motor mounts are probably the easiest to check, but require 2 people. have someone inside "driving" the other is looking and listening up front with the hood open. the "driver" is hard on the brakes and goes from D to R. with good mounts the motor will move some. with bad mounts the motor will move more and there will probably be some "clunking". A stearing stabilizer might help mask the problem, but not cause it. my stabilizer started leaking 6 years ago, and I've never had an episode like yours.  

Personally...I wouldnt take my stuff to sears one bit. Also with that, deffinatly check things out. You never know what could have broke since then or maybe they didnt tighten some thing up. So time to suit up in the work jeans and hoodie and start crawling under that Jeep and seeing whats wrong. Deffinatly check all the mounts and U-joints.  

WEll is your jeep stock or lifted? if lifted then tell us about the lift. I mite be death wobble. Also does it do this at certain speeds? also have you thought about a broken tire belt ortires that are not balanced?  

Good point... but i am wondering, what in the hell is the "death wobble" I used to have another truck lifted before my grand and neither have had any sorta wobbble to them, so what is this death wobble??  

I had this problem at one time. Basically the dealer messed up the alignment and the tires wore funny. ONce I replaced the tires it fixed it.  

I had a similar problem in mine at low speed due to busted belts in my tires and another do to a busted part in my front carrier.  The problem in my carrier though sounds more like yours then the tires.  Just jack it up and pop the covers on your diffs and rotate the carrier if its like mine it will be very obvious that its the problem. I could actually watch the shaft running through the spiders wobble and it eggshaped the whole in my carrier.  

sounds like the front trac bar is going bad or the truck is lifted leaving a bad angle for the front. if its not lifted you can check it easily a couple of different ways.

1) with truck running and someone inside holding the wheel straight push side to side on the fender and watch the body and axle. they should stay at the same angle. if the body moves and axle stays put the trac bar is most likely bad.

2) jack up the front end so tires are off the ground. grab the track bar (usually goes bad at the pitman arm) and push up and down side to side ANY MOVEMENT IS BAD!!!!!!

trac bars are easy to replace and cost about $50 at your local auto parts store. Dont forget to change out your steering stabilizer too.