That's kinda oppisite of what I heard, and I can sorta prove it. Though, I do remember doing that a few times(with my rig, a tractor) and getting out to brag about it, I did manage to burry a 4 wheel drive John Deer 7810. I speeded up fairly good, but bogged down. I learned 2 things, avoid standing water in a field, and don't keep spinning the wheels if you do bog down, that only makes it worse, plus you really get a sickening feeling, and your leg starts twitching uncontrolably. It probly didn't help that I was carrying a fully loaded manure spreader. In retrospect, I could have probably gotten out if I unhooked, but that would have been tricky too. Anyway, it took another 4 wheel drive tractor and a smaller 2 wheel drive to finnally get it out. Fame is mine! I hope to avoid that with any truck I get.
Anyway, I heard that the deeper the mud, the lower the gear. Thats from the June '03 issue of Field and Stream. He also says not to floor it. But, I think I'll listen to youre Idea, it helped me more often than not.