Hi guy's, at least thanks for the moral support!
Well... if I can fix it with a microcontroller and a GPS module that will cost me about 30 / 40 euro's hardware and some hobby time. And a nice extra is that I can have accurate speed readings. The speedometer was about +6km off.
If I need a garage to fix the whole gearbox just for some stupid magnet misalignment it's probably going to cost me into the thousand euro's. And if I'm going that far, it probably wise to overhaul the whole gearbox and pressure plates as well. Don't want to know what that's going to cost.
But, maybe to washers on the sensor to pull the sensor a couple of mm out of the gearbox is enough (it worked before this way) and the only thing I need to do is put 12V on the sensor. But without confirmation I'm a bit afraid to put 12V on a sensor that sends a signal to a 5V ECU. I have the garage manual, but can't find any schematic about the VSS or fuse too the VSS
I've managed to program a microcontroller and control the speedometer. The frequency of the pulses are way higher than I expected.
9 km/h (Real speed) / 10 km/h (Display speed) is 191 hz
194 km/h (Real speed) / 200 km/h (Display speed) is 4125 hz
... and, have you ever seen this on your display?