I have 2 bikes - one with a full Shimano 105 group and the other a full Shimano 600. Both are fully tuned-up and have new grease and ride great.

But my 600 equipped bike (Basso) is just deadly silent when pedaling. I mean no mechanical noises whatsoever. It's a real pleasure to ride. My 105 equipped bike (Miyata)also rides and shifts very nicely, but there are more mechanical noises when I pedal and a very slight squeak coming from the drive-train. Nothing at all disturbing, and most people probably wouldn't even notice it and think it was normal, but when compared to the Basso, you can hear it.

So I know it's tough to diagnose this over the forum, but what causes mechanical noises in the drivetrain? The RD, hubs, BB or maybe a combination of everything? Or is it just the 105 is a step-down from the 600?

Thanks!