ok i thought you meant it revved up to max rpm when you were trying to get it to go but it just sat there, didnt realize you meant it starts revving on its own. i really dont know what to tell you about that. when the truck is running fine how is the idle, does it try to move the truck? just wondering if its set alittle high and then when something fails and theres no load on the engine it starts to rev really high, other than that all i can think of is you say it just revs out, is there something wrong with the trans/receiver? maybe its glitching? the gear shifter ( for reverse) if put right smackin the middle would cause the truck to act like its in neutral, i was just wondering if maybe somethigns going wrong with your receiver pack and its pegging the throttle and putting the shift servo in neutral. i guess thats a long shot for something like that to happen, maybe someone else might know better.