My 88 735i has a life long recurring trans prob. Rather than shifting smoothly, the car shifts with a clunk. This coincides with the gas mileage gauge failing. i.e. the needle wanders. It behaves exactly like a vacuum leak but I'm told that this is an electronic issue. The prob. comes and goes sometimes in the same day. Does anyone know what part is failing and how I might prevent it from failing in the future?