In the meantime I've figured out the required K-Value and the speedo is off to VDO for refurbishment. If you ever want do this you must calculate it as follows: 1000 (meters or 1600meters for mph/h) : dynamic Tire circumference (standard 036 wheels 225/55 r16) is 1,994(m)=501.5 (wheel revolutions per km) * 2.65 (wanted diff ratio) =1328.99 * 4 (segments on the speedo pulse wheel inside the tranny) = 5316 pulses per km = wanted k value