Spin em a little faster! They should self-clean with them huge sipes between the lugs. I've been in some pretty sticky clay in my time but my muds have never clogged up.
I think the idea of the mud is the weight of the vehicle pushes the exesting mud out and grabs some new mud every revolution.. So it may APPEAR to be clogged but it is new mud every time it goes around.
With an AT the mud does clog and cannot come out in the same way.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

professional bovine relocation specialist