Here's a great thread about it:
Been staring at the FSM and the videos online trying to plan out the tc regear. Do I have the right things highlighted? Doing both the 3.1 and the underdrive. This is @cruiseroutfit 's great chart with me marking up the chart with some colors for reference in the diagram (green is changed for...
forum.ih8mud.com
If you do it as a DIY project, it is not for the faint of heart. Also check out the Timmy the Toolman 4 part video series on YouTube with Georg from Valley Hybrids. I did the low and high range gears. It's the biggest improvement I've made to my rig, for sure.