Gear shift sensor using a strain guage by KA Sensors.
 
This sensor has been developed over many years to be relaible and temperature compensated. M8 left and right hand threads make it easy to mount and adjust. For flat upshifts and blip downshift a strain guage type of sensor is essential
 
1000N range
input voltage 5 volts
output 0.5 V - 4.5 volts.  2.5 volts at rest.
GSS-1000-4L8-000
 
Full specification is on the KA Sensors web site here