This is done with a new summit bone stock. All you will need is playdough. Sorry i don't have pictures.
1. Take the tranny out and flip the gears. You will turn it from low torque high speed to high torque low speed.
2. Next open up the front diff and stick playdough or ofna diff lock in it.
Now you will notice a decrease in speed and an increase in crawling ability. Hope this helps for the new to rc people.