Check the axleshaft u-joints while you are at it, they can make a squeaking noise as well And since you are in there grab the tire at the 12 and 6 o'clock position and give it a pull/push. See how the bearings and ball joints are.
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'89 XJ 4" lift, Warn Combo mount and 9.5ti!
31s, 4.10s and rear lockright!
That's enough(for now!)