Dead Box

ive dun it again posted my Q&A on intro page never mind here goes again thank you to those who said hello and welcome now my question was my p38 40 ltr is playing up badly when i select drive some times it will pull off in D with D on dash or it pulls of with gb fault on dash or it wont pull at all and ive got no reverse at all ive changed gb oil and cleaned filter for same seems no different could it be an electrickery problem or do i need a new lackey band i dont mind (much) that it only does 12 to the fiver i just need to drive it its no fun listerning to an oil burner all the time