speedometer incorect reading

[mitchell burke]

hi
i have a 328i and i have put the m3 speedometer in it and the speed is incorect how can i fix this problem do i just need the m3 senser on the diff????
and is the diff on the 328 the same ratio as the m3

[KC Ron Carter]

M3 sensor sets in deeper but the output is the same.

The sensor measures the output of the differential wheel turns so only wheel size will cause any issues.

Later,