JKs disable the traction control in 4lo if you want wheel spin. In 4hi, you can depress the ecs button for 7 seconds to disable it. There are lots of different modes with JKs though. Some methods only partially disable the traction and stability systems.
'93 YJ, 4.0, AX15, Aussie locked D30/open 8.8, 4.10s, 2.5 OME lift, 31s...