it matters if the road speed is calculated via the gearbox output shaft's speed via the speedometer pinion and gear rather than bieng a leccy device like on the auto trans!!!
but on further reading
Speedometer:
The signal to activate the gauge is originated at the
ABS wheel sensors, transmitted to the ABS ECU
(Z108) which then puts out a usable signal to the
Instrument Cluster (Z142) of 8000 pulses per mile or
4972 pulses per kilometer. The signal is also
transmitted to other ECU’s, such as the Engine
Control Module (ECM) (Z132) and the Cruise Control
ECU (Z121).