OK! This is my 2nd session with my GST (1st was during broken in). While having fun in the sand, and after my 3rd tank, suddenly, there's no engaging of the gears. The truck does not move even I rev the engine. The engine clutch and the bell did engage, the pinion gears and the spur gear work great! All 4 wheels are not lock. Brakes are ok! So what could be the problem. I suspect the Forward/ rear shifter are not engage properly. I have use the reverse a couple of time before this incident. Please help!