Maybe I need to explain this better. The intent isn't to get you unstuck when you're up to your mirrors in mud. Think of it like this:

You've changed out your stock hubs for manual lockers and you're goin' wheelin'. You lock 'em in and go through mud hole after mud hole, and now you're miles (or kilometers) from civilization. In the middle of the next hole you come to an unexpected stop, and find that even though your hubs are locked, you only have the rear wheels spinning. After your buddy pulls you out (cuz I know none of us ever go wheeling alone <img src="/forums/images/graemlins/shame.gif" alt="" />) you realize you grenaded a hub. No problem, it's guaranteed for life! Except now you're out HERE, not at home; and while the truck still moves with 2wd, there's no chance that you're going to make it back to public roads without both drive axles. So now your truck gets to spend some quality time with the wildlife in the middle of nowhere while you ship your broken hub back to the manufacturer and wait for a new one. <img src="/forums/images/graemlins/baby.gif" alt="" />

You're more likely to break a hub crawling rocks than mudding, I think, but you mentioned mud so I ran with it.

I've heard of people with other vehicles carrying their stock hubs along while wheeling for just such a purpose. However, I think nearly everyone here changed their stock hubs to aftermarket ones because they didn't work at all, not because they were a weak link. What I've done is to permanently lock the hub for emergency use. Kind of like a space-saver spare tire. It will get you somewhere so you can fix it properly, but it's not for everyday use.

And currently this is for the vacuum lock hubs, not the auto-mechanical ones. But, if someone has a mechanical hub I could experiment with, let me know!