Auto gearbox problems - electrical?

[Tel2]

I have an A6 2.6 SE auto 1995 ... it has been a great car but just started a strange problem last night. I think it is to do with a management module or elecrical problem as several other things occur as well but it is the auto gearbox which is the big problem.

When you first start the engine in P the gearbox appears fine. You can change to R or D and it starts perfectly i.e. the clutch engages correctly. When driving it will change from 1 directly into 4 and then refuses to change down again. When you stop, the clutch will not disengage so the engine stalls. When you restart, it is fine again at the beginning i.e. clutch working but goes through exactly the same sequence, 1 to 4 then stall on stopping. You can't change the gears manually either i.e. from D down to 1, the gear stick has no effect after N.

At the same time, the rev counter has stopped working, after going through a short stage of the needle jumping up and down, and the oil warning light flashes on the computer screen.

It seems to me that an electrical component has broken down either in a management module for the engine/gearbox or some other component. I am wondering whether the fact that it is registering zero revs is what triggers the clutch not to disengage and triggers the oil warning light to come on.

Anyone any ideas please?

[jeanmooij]

I have a 1997 Audi A6 C4 automatic 2.6L V6 mileage is about 115K with a simliar problem to above: Sometimes (say 2 days out of the last 3 days) while driving the oil warning light comes on triggering 2 problems (there is however enough oil in the engine, but I am unsure about oil level in the transmission):

1/ a partial cluster failure (the rev counter goes up and down erratically from 1000 rpm to 3000pm & back then goes to zero while engine is turning fine (actual rpm are smooth) and sometimes speedometer goes to zero while driving and the ln.2 error code comes up indicating I need a service (which I had 5000 miles ago). Other times all 4 warning lights come on at the same time coolant+brake+oil+petrol)
2/ the transmission starts acting strange - if engine is in second gear and I slow to a stop the engine cuts out. Also there is loss of power and auto gear change up from 0mph happens at higher revs than usual (say 2300 instead of 1900)

I think there are 5 possible causes, any advice appreciated
A/ transmission oil must be replaced/topped up or transmission failure (unlikely since why would this cause problem 1?)
B/ ATF Pump Bushing as per Audi A4 Automatic Gearbox Problems | eHow (http://www.ehow.com/list_7676373_audi-a4-automatic-gearbox-problems.html)
C/ Electronic Control Unit Failure as per link B above or corrosion of the main wiring loom (This is more likely since it seems an electrical problem combining 1&2 above - and solution described here Dashboard / Auto Gearbox problems (http://www.vwaudiforum.co.uk/forum/showthread.php?3179-Dashboard-Auto-Gearbox-problems) )
D/ faulty Cluster (This is likely since it seems an electrical problem)
E/ Oil filter blocked causing reduced oil pressure (unlikely since filter was replaced 5000 miles ago & this doesnt explain issues 1&2 above)