I would first pull the fault codes from the transmission to give you a little more insight. You can do this yourself, a "how to" is described on this page:
transmission fault code retrieval As far as swapping the transmission for a manual gearbox (five or six-speed) is concerned - this is a major piece of work. You`d have to swap countless parts that are best taken off a donor car, so you`d need to find one first (and this is definitely not easy in France, as they are extremely rare. Believe me, I`ve had trouble with the authorities trying to register my `91 6-speed in France) . For further information, you might want to contact Ronny Enzmann (
audiv8_32v@gmx.de ) who has done exactly that a few months ago. Read his description here:
automatic to manual transmission conversion If it turns out to be the transmission and you want to put a "new" one in, I 'll gladly assist you to locate one in Germany and ship it from France, as I live in Strasbourg and these things are lots cheaper and easier to find in Germany just across the border. Good used transmissions run around 400-500 euros in Germany.