Yes you can replace just the air bag. The question would be why though? The shocks wear out and very likely will need to be replaced soon anyway? The dealer will probably tell you that you must replace the assembly as a whole but British Parts of Utah has just the air bags...BTW I have removed the airbag from the strut and it is pretty easy. If you do go that route just make sure you pay close attention to all the the little o-rings that seal it up...