Depends on your gearing and how thick the mud is. I used to run a 77 chevy though mud pits with my friends back in high school. If it wasn't really thick we kept it in 4 high, but also went through really fast. In thick stuff it was always 4 low. By thick I mean like the consistency of wet cement, so if we used 4 high the transmission would have blown before we left the pit.
1992 YJ Wrangler 4.0L, NV3550, 2.5" suspension lift, 32" BFG M/Ts, lots of other cool stuff
RED JEEP CLUB MEMBER #494