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 9398 4x4 Crawler Instructions, Technic
9398 - Lego Technic 4x4 Crawler - Page 40 - LEGO Technic, Mindstorms, Model Team and Scale Modeling - Eurobricks Forums
Amazon.com: LEGO Technic 9398 Rock Crawler : Toys & Games
LEGO MOC COOLER 9398 4X4 CRAWLER by Pruisisch Blauw | Rebrickable - Build with LEGO
Lego Technic 4×4 Crawler (9398) - Yuppie Gadgets
LEGO TECHNIC: 4x4 Crawler (9398) for sale online | eBay