When its in 4lo I get an intermittent popping sound from front passenger side. doesn't happen in 4hi or 2hi. Just replaced both front axles, both front hub bearings, new thrust washers, and front end alignment. Upper ball joint on passenger side also replaced. Its more of a (not sure how to put it) slamming sound thats fairly loud sometimes happens alot, sometimes not at all. I dont believe it is related to strain on front differential, because it did it today and i was on fairly flat muddy surface barely pushing the gas. any ideas would be appreciated.

 

I just thought i should add that i had problems with my 4-wheel drive when i first bought the vehicle last month. My friend who also happens to be an ASE master mechanic took it apart for me and a gear of some type was eaten at a little so he re-tooled it best he could and put new thrust washers in. Since then the vacuum switch on the transfer case stuck, and i had to buy a new one from the dealer. (tried auto parts stores and all the switches they offer leaked where the hoses connect. i looked it up, something about 2 different styles of switch, one with larger connector or some such.