I have a 2012 f-150 Lariat with the 5.0L engine and i am having issues when i full steer in reverse. When i back up and steer all the way in either direction, I can hear a clicking/knocking sound coming from the drivers front wheel well. This issue does not seem to occur while driving forward. I have not lifted it or put oversized tires on that could be rubbing either. I have taken it to a ford dealer and they couldn't figure it out. They even replaced the axle in an attempt to repair it but nothing has work so far. Any thoughts? Thanks

 

Sounds like a wheel end problem if it's doing it consistently. Did they lube the CV axle splines when they inserted the new axle?

If it's a thud or what not, only once, then I'd say ball joints.

Hard to tell without looking at it.