Shimmy at 55 mph

Here's the background. 96 XJ 4.0L Automatic w 4 1/2 inch lift. 32x11.50 tires on 15 x 8 AR-39 rims. The thing has run fine as long as I've had it (2 yrs). My son has been using it as his daily driver while we put a re-manufactured engine in his 87 YJ.
About two weeks ago, he told me that there was a bad axle u-joint on the left side. A week ago I went to replace the u-joints and found that the right hub bearing was totally shot. So I replaced both hubs and both u-joints.

Now there is a shimmy that only shows up between 55 and 60 mph. It never had this before.I plan on a front end alignment and all- around tire re-balance. What else could it be?

Make sure the 3 bolts that hold the bearing assembly in are tight all the way.

Also try moving one tire to the back, one at a time, and this will tell you if it is in fact a tire.

Typically, a shimmy at 55 points towards a wheel balance issue. Perhaps you threw a weight?

Try rotating the tires, fronts to back, and see if that clears it up. If so, then go for a wheel balance.

It's a cheap diagnosis to perform, other than some time involved....