One our our friends Olaf suffered a classic SW20 speedometer fault rendering his car unroadworthy. The plastic speedometer ring gear had broken off the differential, giving sporadic readings to the cluster.
We used our 3D scanning to engineer a bracket mounted to the rear knuckle. This allowed us to use a hall effect sensor to read the axle bolts as they rotated, generating a working speedometer signal.
Unfortunately, the axle bolts created a different frequency pulse to the original speedo sender, so we had to purpose engineer a circuit board to translate the signal into an accurate speedometer signal.