this was a backup digger, the motor blew in his normal one, i saw this one the afternoon of the event, it was mearly just attached so people could sit in the truck(thats why there is no door either)
as I said in another comment this was not the normal truck, it was at the event only to be sat in by fans, but when Dennis blew the motor in his normal grave digger they had to resort to this one, i believe this one was rolled the week previous and they just didnt bother replacing the body, because they thought it wouldn't be needed.