My automatic gearbox will not pull away in D but will manually in 1st and you can gather momentum and shift all the way up to Drive eventually. I self diagnosed this as a blown gearbox? Am I correct? Problem is I've now purchased a donar vehical which drives fine until you put it into low ratio and then it vibrates and just doesn't sound good when you gather any speed / revs whatsoever. Could this be the transfer box? Between the two faulty vehicals could I make one good? Any help would be appreciated.