My truck was in the shop for 2 months without resolution. The mechanic says the front end is tight, engine mounts are tight, transmission mounts, etc... but at times the front end of this truck makes a pop sound loud enough to wake the dead and feels like something that was binding released. The upper control arm was replaced about 1 year ago and everything else was checked. I am not sure what it could be. I thought it might be body bushing but I could not see how they could cause an issue on and off and cause it so bad that at times you can feel it through the steering wheel and front end. At times you would expect noise (driving on bumps, rough road, potholes, very deep rut or even my rough driveway as an example) it does not do it. The first time it did I was on an uneven driveway and heard a pop sound but thought nothing of it. Now it has become dangerous to drive because I have no idea when it will happen. When it happens it is not always the same thing. Sometimes it will be a pop you can barely hear. Much of the time it does nothing at all. I drove a 6 hour trip on the interstate and back roads with nothing happening. Drove 30 minute round trip tonight and didn't know if I would make it home.