axle differential BM028 vs BM072. Whats the differences?

[cidos]

Dear beemers,I have a question regarding the rear axle lah. mine e46 328 year 2000 is using axle code BM072. one friend of mine if offering to sell his axle code BM028is anybody has any idea what this code stand for. and if i install this new axle. whats the effect. actually i planned to change the axle since expecting its not working very well. bunyi bising and dup dup sound lah. thank bros !!!!