cococola

I've just put my new mgf steps peed on the road and the car drives well except for a noise that comes from inside my gearbox pulling away and at low speeds. I can only describe the noise like a slipping alternator belt noise. The previous owner had the gearbox replaced and the correct gear oil put in and the gearbox certainly looks nice and fresh. I wonder if it is something that would settle down as the car has been stood in a garage for 2 years or is there anything that I can check or repair please?
I love the car and being older now thought that it would be a good thing to replace from my manual mgf. I realise that the gearboxes were not the best but thought that this one would be good.