hmmm...i'm not sure having more weight in the bed helps in mud in 4wd. i think it helps in 2wd because it changes the weight distribution so it is more over the only drive wheels. but in 4wd, i don't think that's much of an issue because the entire weight of the truck is over drive wheels (ignoring the ramifications of open diffs).

my totally unscientific personal obversations are that smaller, lighter trucks do better in mud than bigger, heavier trucks because the heavier trucks sink more.

based on this, i would think you would want to be lighter even for mud...unless maybe it is shallow mud and you can sink all the way to the bottom and find good traction.

having said all that, i have a cap on my pickup and prolly 300 pounds of tools, gear, and spare parts in the bed. <img src="/forums/images/graemlins/shiner.gif" alt="" />