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So it looks like it is my turn for gearbox woes. Car had been driving fine with no prior symptoms but on the way back from Cornwall approaching a roundabout revs rose but no forward motion. I switched into manual mode and there was then an almighty clunk before PRNDS lit up on dash and car started pulling away. We made it home in 'limp mode' which I believe only allows 3rd and reverse to be engaged.

I have since scanned, cleared codes, driven car and scanned again, only one DTC being returned (posted below). Car now starts fine but as soon as 'D' is selected and accelerator depressed nothing happens for a few seconds then there is a loud clunk and PRNDS lights up on dash and car pulls away and remains in third gear. reverse can also be selected.

Car is on 133k miles and had the gearbox fluid changed on 67k when I bought it by MRC who have maintained the car ever since. At the time it was commented on that the old fluid was as new. MRC are rammed at the moment and some distance from me so looking for alternative options.

Questions
1. Is it possible to check ATF level/quality without draining the whole box?
2. I noticed some damp on the passenger carpet up by the glove box. MRC spent a long time fixing wet passenger foot well when I bought the car. I've checked the scuttle drain, pollen filter and rear washer working OK, so thinking this might be a blocked AC drain. Could this fault be electrical and if so what should be checked?
3. Any recommendations for competent indie in Maidenhead/Berkshire to inspect car?

Thanks

17114/P0730/001840 - Gear Ratio Monitoring: Incorrect Gear Ratio

Possible Symptoms
## Malfunction Indicator Light (MIL) ON

Possible Causes
## Transmission Fluid contaminated
## Transmission faulty (Mechanical Problem)

Possible Solutions
## Check Transmission Fluid (Color and Contamination) ## Replace Transmission Fluid when necessary

## Check Transmission Mechanics

Special Notes
## Transmission Damage may be caused by Engine Problems, make sure there are no other/relevant Fault Codes stored in Engine Control Module.
## When found in 6-Speed Automatic Transmission (01J/Multitronic): ## Instructions on how to check the Transmission Fluid as well as Details on a special Test Kit can be found in TPI 2016661. TPI 2006088 may also be relevant.
## A conversion from 6 to 7 Clutch Plates may be possible. See TPI 2004856 for Details.

## When found in A4/A6/A8/S6/RS6/S8 models with the 09L, 09E or 0B6 transmission that have DTCs: P0730, P2700, P2701, P2702, and P2703: ## RoW (Rest of World) Market customers can see TPI 2020766 which pertains to slippage due to the ATF filter.
## NAR (North American Region) Market customers can see TPI 2021292

That doesn't sound good and probably not electrical/damp or the F125 switch.
Fontain in Iver might be worth a call?
I guess a check on fluid level first.

The TCU is under the carpet there. Pull it out and see if it got wet.

Fix that leak. Probably the bulkhead drains blocked and/or air intake seal.

Slipping and banging into gear is never a good thing. It's almost as easy to change the ATF as it is to check the level but it's up to you.

To check the level (ATF must be less than 30 degrees), start the engine, open the fill hole and wait for the ATF to reach 35 degrees. If it starts to drip out at 35 degrees te level is correct. Obvs the car needs to be level.

/just saw you checked the bulkhead. Could be AC drain. Seen it happen.

You'll need a Vagcom to monitor the temp of the ATF.

Thanks for the input, will have a go at getting the carpet up at the weekend. What needs to be removed, glove box, door sill trim? Any pointers appreciated.

Bottom a pillar trim, door runner trim then you can prise the carpet up enough to get at the TCU housing. I think I posted some photos a looong time ago.

TCU was what I needed when I had the same issue.


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As I've only got the one DTC to go on and how the car is behaving is it possible to remove TCU and test it? If so can this be done by any garage or would it require a specialist? Just trying to narrow this down.

Thanks

I can't think of anyone that could test it with any degree of confidence. Too many horror stories for all these ecu repair places.

I personally would source another TCU. If it's that, great. If not then you've got a spare and it'll always be worth what you paid for it.

PolarSilverX50 wrote: ↑

Fri Sep 14, 2018 10:48 am

As I've only got the one DTC to go on and how the car is behaving is it possible to remove TCU and test it? If so can this be done by any garage or would it require a specialist? Just trying to narrow this down.

Thanks

The ECU Doctor is very good. You can send them your ECU/TCU and they will test it for free. If it needs repairs then they will give you a quote. If it doesn't then they will ship it back to you.

Update - I finally got some time last week to remove the TCU which turned out to be surprisingly easy (1 hr tops). It was sent to ECUTESTING who have rebuilt the car's ABS/ECU module successfully in the past. Just got an update from them - they test/repair these units regularly but couldn't read the software on my TCU so it's being returned with no charge.

I'm going to contact the ECU Doctor PipRs6 mentioned next and see if they think they will be able to test it. I also contacted MRC as the car has their stage 1 engine/gearbox map but they have confirmed that there's nothing in their gearbox map to prevent accessing/reading the code.

Audi have quoted £1200 + VAT for a new TCU which I'm happy to pay but want to be 100% it is the TCU first.

I'm going to start looking on Ebay, etc, but if anyone knows of a TCU for sale/RS6 being broken please let me know.

Thanks

There is a c5 rs6 on ebay that is being broken at the moment, came on in the last few days...

simonpoulton wrote: ↑

Tue Oct 02, 2018 1:38 pm

There is a c5 rs6 on ebay that is being broken at the moment, came on in the last few days...

Got a link?

simonpoulton wrote:There is a c5 rs6 on ebay that is being broken at the moment, came on in the last few days...

Boys be careful about that car as it’s a bit of a shitter!! It’s done well over 200.000 miles and when they tried to sell
It a few years ago I know it had a gearbox fault as I was tempted


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If they are easy to remove then it might be worth seeing if there is someone near you who wouldn't mind you borrowing their TCU for 5 mins to test in your car. If you are taking it from a known working car and it solves your problem then you know its the TCU!