Reporting in with the same problem, same speed. Seems somewhat dependent on road surface (less severe on concrete which is less likely to warp and deflect vs asphalt).

It did it to some degree before I lifted, worse after lift and new (used) tires. Went in for a alignment since I did a T-bar crank (not full) and they said the lower ball joints were bad.

They seemed to however base this on tire wear, which I told them were on a different truck previously. Waited because I want a second opinion. Crawled under the truck and the bearings look fine, if not almost new, however since they were attached couldn't check how much play they have. Had U joints replaced about 10k miles ago, wheel bearing assemblies at the same time.

Seems could be common problem, any insight?

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2003 XLT 4.0L V6 4x4
Mods:
2" Lift (T-bar crank & rear spring helper leaf), 33", Dualer AT's, 130 amp Alternator, Moog Sway bar link, Silverstar zXe headlights, JVC Stereo bluetooth/usb w/o cd deck