I'll fix your trip odometer for $40 if you send it to me. It's a very simple fix. I've done a few with great success. There is no need to replace all the gears. Do a search, you can easily fix it yourself.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked