DIY Gearbox output flange seal replacement 018 409 399 B

[skyegtb]

Finally got round to replacing my leaking output flange seal part number 018 409 399 B, cost in UK £14. The seal had been leaking for at least 6 months and I found a couple of drips of oil under the middle of the car if I left it parked overnight. I didn't top up the oil during the 6 months it was leaking and for info discovered it had only lost about 180ml of oil in that time.
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Anyway, the job itself is pretty easy and straight forward. I followed the excellent guide over at audipages which has a full guide for a 4.2 Audi A8. There is very little difference between the A8 and the RS6 apart from the downpipes.
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http://www.audipages.com/Tech_Articles/auto_transmission/transealreplacement.html
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Here's how I did it:
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1) Lift car off the ground. I have a car lift which makes this job (and all others) much easier, but I guess it could be done with axle stands although I would not particularly wish to do the job that way!
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2) Remove exhaust back boxes and center pipes. I have the MTM exhaust which I believe is slightly different in design to the stock exhaust. Note that the downpipes should be secured from below to stop them dropping too far on the flexi-joint.
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3) Remove the 3 heat insulation panels from below the main driveshaft
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4) Remove the protective plate from below the driveshaft joint at the back of the gearbox
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5) With the car in Park and the handbrake on undo the 6 bolts that secure the driveshaft to the output flange. You will need to release the handbrake and put the car in neutral to turn the driveshaft to get the top 2 bolts though.
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6) At this point I removed the oil fill and drain plugs and drained off the oil in the box, there was about 700ml in there and the spec says it should be 880ml when full. I had lost around 180ml in about 6 months
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7) Use a rubber mallet to tap the driveshaft off the flange, then move the driveshaft to one side (it will rest on a downpipe - I put a bag over the end of the driveshaft to stop dirt getting on to the grease there).
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8) For more space remove one and loosen the other bolt on the central driveshaft bearing to allow the driveshaft to be moved further away from the flange
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9) Undo the single T40 torx bolt that holds the flange to the rear of the gearbox and remove the flange, the seal is now fully visible
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10) You can now pry out the old seal with a wide flat tipped screwdriver but be very careful not to damage any of the aluminium faces. I personally used a small block of wood to pry the screwdriver against to save any potential damage.
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11) After cleaning everything up I now fitted the new seal. I lubed it up and gently tapped it in with a nylon hammer then used a 38mm (IIRC) socket to tap it just inside the hole.
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12) Finally I refitted the drain plug, filled 880ml of oil and re-fitted the fill plug then put everything back in the reverse order to how I had stripped it. All in all about 2 hours work and since doing it everything is leak free again
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