Z3 Speedometer error
I have a 1999 Z3 speedometer is about is about 8 MPH slow, I have checked it with my GPS, also the car has a trip computer which displays the same speed the Garmin GPS does. I feel like the sending unit in the differential should supply the same signal to the trip computer as well as the analog speedometer. I believe the instrument cluster has been changed out at some point in time, prior to my purchase.
any suggestions or thoughts on the error.
Thanks for any information.