Jeep: Jeep Shakes, jeep yj, gas tank sending unit

Question
Hi there.  I purchased a 90 Jeep YJ a few months ago and have had a few run ins with the "shakes" on the highway.  The jeep will shake very violently for about 10-20 seconds or so and then stop. It has done this a few times on the highway.  The first time I thought I had blown a tire.  I thought maybe it was a certain type of pavement or uneven cracks in the highway, but when it happened again, the shaking did not stop when I tried braking, downshifting or even changing lanes.  It has done this a few times and only on the highway.  I had heard that it might be the track bar, the hub. the ball joints or in need of a stablizer.  The person I had asked had a TJ though and said he was uncertain due to the different susupensions on the YJ.  I am just afraid to take it to a shop and get taken for a ride for unneeded parts or repairs.  In general, the Jeep is in very good condition, this is the only problem I have come across.  I know without actually looking at the vehicle it may be difficult to give an accurate diagnosis but maybe you have heard of this problem before.  If you could give an opinion it would be greatly appreciated.  Thanks in advance.

Answer
Congrats on the jeep purchase, the Yj is a blast to own, I will give you some generic info on this vehicle before I try to handle your question. There were a number of recalls on that model vehicle that you should check at the dealer with as soon a possible. First would be the gas tank sending unit seal, secondly the front brake hoses. Third the parking break ratchet. It is very hard to diagnose this condition without a drive or look myself but.  I would swap the tires front to rear and see if that helps could be a radial tire belt. Second thing I would look at is the Track bar, they are what limit the side to side motion of the front axle housing The usual indication of this a wander on the highway and a rattle over bumps in the front. Hope this help for now. I will call around and see if I could get some more insight.