I finally got my truck running and i ramped it and it ran fine then i got home and tried to start it the next day and when i put it on the ground it wont go, it will keep running but wont go, i have already replaced the clutch spring and the gas tank. I think the engine might have shifted and i will try that but i was going to see if anyone else has had this problem and how to fix it.

check clutch spring
it mite have came
apart

Check the slipper clutch. 08013 might have come loose. Alot of people say the gear with the purple nut, but now I have some in silver lol. Tighten that nut if it is loose.