Typically in a stock Rubicon, you would want lockers on, 4lo and if in an auto trans to manual shift from 1st on up as needed to maintain speed and also with the overdrive button turned off.
The day before this video was taken when we were running in the stock class in the EVO TJ, the bottom of Sand Hill is exactly where we broke and the race ended for us, so we had plenty of time to see other rigs break down on the obstacle and also see how not to do it. What should be noted, in this video of EVO1 Mel actually took what is considered to be the harder of the two possible lines on that hill. He had front and rear lockers on, but he's running a 3 speed manual body Torqueflight 727 automatic transmission and an Atlas transfer case. It's not as simple as just 4hi or 4lo. He started in 2nd gear in the auto, but I don't remember what the t-case was in, and towards the top was forced to shift into 3rd to stop some of the wheel spin from the 6.1L Hemi. Hope this info helps out a little bit.