Ultimate upgrade for the 9398 4x4 crawler with pendulum steering (no servo needed). I also made a pendulum steering file in the rebrickable link you can download and have a closer look
LEGO Technic 9398 Rock Crawler by LEGO Technic : Toys & Games - Amazon.com
Lego Technic 4×4 Crawler (9398) - Yuppie Gadgets
Buy LEGO Technic 4x4 Crawler (9398) at Mighty Ape NZ