Based on what I read here, yes it seems to be a common problem. the 4wd/2wd lever is held in place by a ball in a grove on the shift rail that is held in place by a spring. I would check the ball/spring, spacer to make sure it is properly installed. When proper, the lever will "click" into position as you hear the ball drop into the grove on the shift rail. Reasons for the problem could be that the spring is too weak, the shift rail is not travleing far enough for the groove in the rail to get under the hole wiht the spring and ball in it. or the spring and ball could be missing, or just the spacer which puts more pressure on the ball could be missing. Or the rail could be improperly installed so that the groove does not line up with the ball/spring/pin assembly...