The new gears are nylon or plastic whereas one of the original gears was made of a more resilient clear plastic. I believe the new gears are the source of the click-click noise and I haven't been able to find a set of gears that are made of the same material as the original gears. Mark

Hi Mark,

thanks for your answer. I think what you're describing is exactly what is going on. I found a similar post reporting exactly the same issue:

Odometer Gears--Great Solution, Just Noisy - Mercedes-Benz Forum

So I opened everything again today and took the cover from the magnet and the magnet apart and lubed (with a teflon-based lube) the whole spindle from one side to the other.
Also, I added some high pressure bearing lube to the gears and so far it looks - and more importantly sounds good!!!

Everything is still very accurate (checked by GPS again), so I'm pretty happy now... :-))

Off to the next project.....

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89 300 SE Euro (264,000 miles)