Audi changed the Ur quattro differential locks from cable operation to vacuum control sometime in May 1981 - I have yet to track down the exact point of the change but it was somewhere around 85 B 901 221. This diagram is a schematic of the setup on cable lock vehicles.
Items in green are only fitted to vehicles with air-conditioning
To make things simple for the Monkey Lads™, Audi colour-coded some of the hoses. You'll be lucky to find any trace of this now because the dye will have faded over the years and replacement hoses had no coding.
Colour codes will be listed at a later date
{© IJH 2001}