Speedo jumping

[pr1m3]

 2007 s4rs

The speedo needle is jumping 10-20 mph when clutchless shifting at high rpm and stays reading incorrectly until I shut down and turn the key back on and the needles do their sweep.  Any idea why this is happening and how to correct it?

[Dirty Duc]

Short in the taillight power wires... like one of them has rubbed the insulation off.

when you bang the shift, the seat moves the taillight momentarily to allow a little bit of arc, which upsets the instrument panel.  They are on the same circuit.

[pr1m3]

Short in the taillight power wires... like one of them has rubbed the insulation off.

when you bang the shift, the seat moves the taillight momentarily to allow a little bit of arc, which upsets the instrument panel.  They are on the same circuit.

Not sure that's completely the problem. I removed the entire tail light assembly for a track day and the speedo was still jumping...

[Dirty Duc]

Huh... maybe there is some other place where a wire has rubbed a raw spot in that circuit.  I understand that sometimes the wiring harness by the headstock can be problematic as well. 

[Armor]

Check the wire going to the sensor, by the wheel.