RE: Help with Genesis shifting (into neutral?)
What it sounds like, is your center outdrives (set screws) are loose. In the front and rear of your truck, there are 2.5mm set screws that hold the GS093 (rear) center outdrives to the MX037 bevel pinion gear.
If these screw become loose you will experience "free wheeling" as you stated. Check both the front and rear set screws that hold the center drive shafts to the MX037 bevel pinion.
Tighten them with lock tite so they do not come loose.