I know I saw a thread on here before about this issue, but I can't find it. sometimes 4x4 will jump out and back in. it usually happens under load and makes a loud pop because of the stress. it's does it sporadically, no rhyme or reason. it can be under a really hard load and not do it, and it can be a light load and do it. and vise versa. is there a known/common cause for this?