Axelshaft sliding?

Heres the deal,

I've got a 90 z71 and about ywo months ago i noticed a odd noise and foud that the front passenger side axel had slid out. After taking the differential out and replacing a c-clip and a gear that goes over the axel the same thing happened last week. I was sure I had put everything in right and I just don't know whats up? Is there anybody who has an explanation? Any help would be much appreciated

odd, did you ckeck the center pin in the gear cage maybe it is worn unuf to allow the axle to push in far unuf for the c clip to slip off the axle shaft, also some diffs have cone spacers behind the gears if missing or worn this may cause the clip to fall off.