E30 Zone

my 325 in 2nd 4th and reverse is making a fine grinding noise, not unbearable but noticeable. can any one shed any light on this what it may be? i also have a 320i gearbox spare, is it worth while putting this on and will it fit or cause problems? any help appreciated. thanks simon

If you have a 320i box i would use that as 1st 2nd and 3rd are closer ratios, yes it will fit but you will need the prop and gear linkages from the 320i to go with it.