Here's some things to check:
1) Trackbar axle bolt TIGHT, hole still round, correct size bolt, bushings/joints in good shape. Dana axle bracket is a 7/16" hole, bushing is 10mm, and bolt is 9mm. The bushing can be drilled to 7/16" to match, and new hardware installed to tighten this up.
2) Tires balanced? Super Swampers, for example, are notorious for being way out of balance. I use Centramatic dynamic wheel balancers to keep mine balanced.
3) Upper adjustable control arms to set correct castor. A good self check can be performed by placing an angle finder on the flat plate next to the shock just behind the axle tube. (Check each side.) If it's about 3 degrees below 0, you should be OK, less than that and you will likely have some trouble. Here's an example! Here's another! Another way to see what the actual angle is can be performed by placing a large socket on top of the ball joint, make sure it's sitting flat with the joint, and placing the angle finder on top. The drivers side is hard to see accurately because of the diff and the control arms. A mirror and flashlight may make it easier. The digital one works better then the needle one for this test, you can push a button and hold the reading while you extract it from back there.
4) TRE's in good shape, you may even have to disconnect the joints and move them by hand to verify smooth operation. Remember, easiest way to remove TRE's is to hit the surrounding metal piece with a BFH to loosen, don't hit the threaded end or use a pickle fork unless you are 100% sure you don't want to use that TRE again.
5) Solid lower control arms to prevent unwanted movement and flex, if you still have the factory ones they could be the problem.
6) Control arm joints tight, my RE superflex joints can be disassembled, cleaned, lubed, rebuilt, and reassembled as required for only $10 if parts are needed. Alternately I can just tighten them up with an inexpensive tool. RE told me to rebuild after tightening 3 or 4 times. The bushing on the other end can also be replaced for $10 and a few minutes work once the arm is removed.
7) Factory washers on the lower control arm to axle joint. My RE arms came with new washers, so I used 'em. They were slightly smaller in diameter and thickness them the factory, and didn't have the tapered edge to ensure correct axle alignment. Once I replaced them with the factory ones, it tightened things up nicely.
Check the joints in the steering shaft, one under the hood and one under the dash. I had one loosen up, and it took forever to find it. Felt like problems elsewhere in the steering system because it allows play between steering wheel and the rest of the steering system. I ended up replacing my intermediate steering shaft and it was good to go.
9) Wheel bearings (hubs) in good shape? Cheapest I found for my wifes TJ was about $150 at Autozone, made by Timkin, highly respected bearing company. Everybody else wanted around $200. Don't do what the previous owner (idiot!) did to hers, he only tightened the axle nut to hand tight instead of 175 ft/lbs.
10) How about your ball joints? Same goes there, a good way to check is to jack the tire off the ground and see if there's any top/bottom play.
11) Ensure upper and lower shock bushings are in good shape, I had one get cut by a sharp edge on the upper mount, allowed some unwanted axle movement before any dampening occured.
12) Last but not least...check your axle shaft u-joints. I had one that was worn, and it allowed just enough wiggle at speed that death wobble would occur if I hit a bump the right way. This was after putting 35's on, the heavier wheels prevented the system from dampening out the vibes as easily.
Basically do an inspection of every part from the steering wheel to the tire. Verify each fastener fits correctly in the holes provided with no slop. Each time you find a component worn, or loose, and you tighten or correct the problem, your alignment will be off again. Get a factory service manual or Chilton's to ensure correct torque specs. Near the end of ORO's U-turn install instructions, they give a good step by step procedure for doing a self alignment that you can follow. Get it here! I do this about once a quarter anyway just to check. Make it part of your routine maintenance as it only takes about 20-30 minutes if adjustments are needed, only 10 minutes to check.
Stock Jeeps don't have castor/camber adjustments, so many shops will only adjust toe unless you tell them specifically that you have adjustable upper arms, then they'll probably want to charge you more. An honest shop will tell you that the alignment stand may not even read your vehicle correctly, depends on the equipment they have, so talk to the manager.
