Clunk in Front left

[wpresler]

03 explorer XLT 4X4 Couple problems
New is when you go in Reverse and wheel starts to slip there is a clunk. The clunk is drivers side front. I have had this since new but seems to be getting worse. Ford could never find it. What could it be?
The other is tire hum. I changed the front wheel hubs and bearings 6000 miles ago. Thinking it is the back now. The front can't go bad that fast. Could they?
New to site. Great treads.Will be using alot.

 

[Ronin8002]

The clunk is your auto 4x4 engaging. It's normal. If it annoys you there is a way to install a switch to disable it if needed. Do a search for "brown wire mod"

the humming if it is coming from the back could be the differential...something the 2002-2005 models are known for also. Not harmful, just an annoyance mainly.