Weird noise when accelerating from a stop

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I've been getting weird noises and vibration when accelerating from a stop. This vibration occurs whilst acclerating in a straight line and the vibration continues even if I lift off the accelerator. The vibration occurs only at low speeds, maybe upto 10-15 mph. I'm thinking it could be my auto tranny going again even though it shifts great (albeit slow kickdown from 4 to 3). Any help appreciated, thanks.