I was driving down the road today, and it instantly started vibrating real bad when I accelerated, the tires have been needing to be balanced but it only shook around 43 mph, and it was never a constant vibration, but now its constantly vibrating as I accelerate
List of possibles could be quite long but one is you might have thrown a wheel weight. If you had a little trouble before perhaps one was loose and finally tossed. That's probably the simplest possibiltiy. Good luck
Check out my recent thread with the same problem: Yet another mysterious vibration problem!
Cutting to the chase - check the rear u-joints and or the driveshaft itself. You can disconnect the rear most u-joint easily, then slide out the driveshaft. Put the Jeep in 4 wheel high, which will engage the front driveshaft (you'll be front wheel drive only now) and drive the Jeep around. If you don't have the vibration, you've isolated the problem to the rear DS assembly.
Replace the U joints, and reinsert, see if it all works. If not, then the rear DS could be out of balance. Take to a machine shop and have balanced or rebuilt, or buy a new one. Check out Tom Wood.
I took it to Discount Tire today to get the tires rebalanced and they wouldnt touch the jeep, because it had spacers for the wheels, and then they tried to bullshit me into buying 200 dollar rims, so i just had them put the tires back on and i rotated them myself, that worked a lil bit, I checked the U-joints and they were fine, so im hoping once i find somebody to balance the tires that thats the problem
The skid plate that holds the transmission up had dropped a bolt and the others were loose so that could have been a lil bit of the problem also
I've got the *SAME* problem with my (new) 1999 Wrangler. It's got 31" tires, a small 3" lift, and I had the tires balanced and rotated. The problem is not consistent - sometimes mine is much worse than others. At times it doesn't happen and at times it shakes violently. If it stops at 50 MPH goes that indicate something else? I've got a 2.5L engine if that also helps...