In my case, the noise developed over time. It was dead quiet for the first 1000km then started to get noisey. I had 2 problems. the screws holding the final gear were loose but also I discovered some wear on the non drive side rotor shaft. Loctiting and tightening the screw holding the final gear helped but a dab of loctite on the rotor shaft cured the noise completely. I am now up to 2000km and the drive is still dead quiet.
Keep in mind, my drive is an early model and I believe the rotor shaft wear issue has now been resolved (hence my question about the small orange O ring)
However, in your case, I doubt you are suffering the same the problems and more than likely have a QC issue with your drive. So your dilemma is whether to send it back or stip it down. It sounds like sending back would be entail long lead times and uncertain outcomes. With this in mind, I would suggest to open it up and find out what the problem is. The drive comes apart quite easily and if carried out methodically, shouldn't be too hard to find where the noise is coming from.
Over tightening the the 2 main nuts is not going to cause a noise problem. Please carry out the following.
With the chain removed, spin the cranks backwards. Does it spin freely and quietly? (4 or 5 turns after a hard hand spin)
If no, strip down the final drive section of the drive that goes through the bike's bottom bracket.
Next, spin the cranks forward. This will spin both the final gear and the intermediate shaft and gear. Listen for any scraping or unusual tightness. You should get one or two revolutions out of the cranks with a firm spin forward. If not, you will need to investigate further.
Let us know how you go from there.
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