Excessive axle endplay..'01 ST

I recently got my 2001 Sport Trac. Already fixed a bunch of stuff due to previous neglect. Bought new tires and after 4 return visits the tire shop noted a large amount of endplay on the passenger side axle. I jacked it up and checked and sure enough, LOTS of endplay. I have heard about carrier pin wear, wear on the end of the axle shaft, worn c-clip, etc. My mechanic neighbor spoke of a rarely seen but true possibility of a cracked/broken carrier housing. I jacked up the ass end and had the wife put in drive. When she got to abou 30- 40 on the speedo, I heard a 'clunk' and watched the Pass. side wheel jump out about 3/4 inch. Any idea or experiences would be appreciated. I plan to jack it up and pull the diff cover to look this weekend.

I am assuming this is the rear. i know on LSD rears there is always about 1/4" of play because of clutch wear but if its open rear then there could be some concern but not tons i would open the pumpkin and inspect its easy and it will count as a diff service however before removing cover open the fill plug first to make sure you can. the way the diff is designed is you have 2 axles which slide into the tubes and spline into the side gears and then a c clip goes around them and what stops them from falling out is the center dowel pin the axle hits that before coming completely out and dropping the c clips if it moves past the side gear lip the clip falls and the axle comes out now driving and that happens would be bad.

Tom.