Sarah,
It sounds like you may have a hub problem.
Sometimes this can be caused by using too thick of a grease in the hub, not allowing the sliding mechanism to "lock" the hub.
Provided that you have no other issues with axle u-joints, (a seized u-joint cap can cause any thing from a "click" to a violent pull to one side)
The next day you have some time in the shop, get out the manual and tear down the locking hubs.
Clean out all the grease. Look for any broken or chipped parts.
If you don't find any broken pieces, lubricate the hubs and dials with a spray type grease, either white lithium or red grease ( I prefer the red)
If you don't have access to spray grease, use an engine assembly lube.
Do not pack the hubs like you would a wheel bearing, just coat all the pieces so they slide easily.
Re assemble the hubs and go for a test drive.
To check the axle u-joints, lock the hubs and turn the wheels. Jack up the front of the truck, and slowly rotate the tires by hand, if you notice a drag or the tire gets hard to turn, mark the u-joint cap that you can see through the knuckle. Continue rotating the tire, if you get the same drag or if the tire gets hard to turn at the same place, you have a bad u-joint. I have seen u-joints that were rusted enough to actually try and straighten the tires as the axle turned. (this will cause the violent pull I mentioned earlier.)
Good luck.
