“Full” from the secondary drive – after start, at CALTS temperatures

Moin in the round, does someone know that: relatively loud sounds (whole) from the secondary drive range? can’t really locate it, it dives (even last spring, when it was still cold in the morning) right after the engine start up, when “starts up” – and can be heard clearly at the first few meters after starting up…After a few minutes, the whole thing happens gradually, when the operating temperature is reached, it can’t be heard anymore… and only when starting – noises definitely don’t come out of the engine, since NOTHING is to be heard in idle… Please only answers from people who know more… Thank you in advance! Greetings, William