Yes, it is. Usually in VW´s the blue cable is for the illumination of the display and the buttons of the radio. This can be dimmed. This is NOT faxt in the V8. The blue cable is a speed-indicator for the automatic-volume feature. The faster you drive, the louder your gamma or beta-radio will be.
Check what´s up with your blue cable. If it isn´t connected, the failt must be elsewhere. If it is connecten, perhaps to ground, that would explain, why your gearbox doesn´t know your speed.
Greetings from germany/odenwald
Christian
