Tie rod ball joints (the inner part under the boot) can wear out. The easiest test is to jack that wheel off the ground, then grab the wheel at 3:00 and 9:00 and push back and forth - in the direction of steering. There is a little bit of play normally in the steering rack, but if you can get a full degree of movement, then its too much. If both front wheels are off the ground, it may be harder to test, because the left/right movement of you pushing on the tire will actually move the steering rack back and forth and both wheels will turn. Your tire shop should be able to demonstrate this for you as well, if you don't want to jack up your truck in the driveway. Replacement (Toyota branded) parts should be under $100 for each side, but note that they do not come with the jam nut, so be sure to recycle the one from the old tie rod or purchase a new nut.