Wierd Problem with 93

Ok my GF's Xj just started acting up again. This morning i was driving it and it was shifting fine and running fine but as soon as i got up to about 43-44mph it started shaking really bad, like DW but it was not in the steering wheel. when i would let off the gas, it would stop shaking, and then when i would step back on the gas to go faster, it would shake more. We did about a 30 mile trip today and road mostly on the highway. When we would get onto the highway it would shake all the way untill about 55mph then stop and drive fine. now ive never experienced anything like this with mine and its really bothering me. any ideas??

I just went outside and checked under the hood and find a loose vacuum line that was suppsed to be connected to the charcoal canister i guess?? its not the one behind the front bumper but on the passengers side beside the oil filter. started it up and it sounded fine just havent driven it yet.

Could be tires or something on the suspendsion. My YJ shakes and shimmeys once she hits 35. I'm gonnna rotate the tires once of these does. Might have a tire out of rounds or balance.

i thought about that but even though it STOPS shaking when i let off the gas, still going the same speed and then when i hit the gas to continue it starts shaking again????

Auto or Stick?

Auto

Check your U-joints. When you check them for play, make sure you put the trans in neutral and use the E-brake. You will not find any slack as long as they are under tension.

I just completed a 2500 mile trip in my 92, at one point found I had a vibration when under acceleration that was not present when I let off the gas. It got worse as time went on. I quickly checked the U-joints with it in park and found no slack....later checked again with it in neutral and found a bunch of slack!!!

When I got them off to change, there was no bearings left in one cup....just dust!!

Yeah i just got through rotating the tires and checked TB,Drag link, and tie rod. Everything seemed fine, didnt check the u joints, but sounds like that might be the problem. But with my experience with bad u joints, they squeak alot and never had to worry about vibrations. but after some lunch i will go outside and check them all.

went outside and checked for play in the front and Rear DS and the front DS i was able to wiggle and the rear DS was tight and wouldnt move, so im guessing the 2 u joints in the front ds are bad? and thats whats causing the vibrations??? Everything else looked fine other than the drivers side warped rotor.