When operating my X2 in reverse I notice a loud clicking sound .. I don't remember if it was there before, should there be clicking like that?

 

Check for play in your rear wheel bearings but it is most likely the rear prop shaft. It develops a little play over time.

 

sounds like an axle or diff. problem to me

 

Sounds like a cv problem to me.

 

oh boy, this sucks

 

front end or back end? if its a cv joint they tend to get louder under more presure like going around a corner or in awd if the front. check the cv boots for rips to see if its that one or not. usually water and mud get in a bad or loose boot and will eat the cv joint.