Torque Converter finally gave up.

4.2 V8 40v biturbo - 450 bhp
4.2 V8 40v biturbo - 480 bhp (plus)
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Cunningstunt
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Torque Converter finally gave up.

Post by Cunningstunt » Thu Sep 11, 2025 7:48 pm

Hello all!

Long time lurker. Bought my saloon off here in 2017, I think I'm its 3rd owner off the forum actually. I've loved every second of owning it, was my daily driver until covid hit. Since then its been sat in my garage on a trickle charger(Always something else needing money). Finally got around to getting her out and on the road. Fired up first time (followed advice on the faq) with no issues.

Its been at the mechanics getting everything I could think of done to it over the summer, and of course on the way back from the MOT centre (passed) last week it decides to start slipping in 3rd around 3000-4000 rpm. Flushed the gearbox oil a few more times to see if it would help but it then threw up fault code P0741-Torque converter lock mechanical failure. Oil seal in the TC perished over time? Not surprised it happened, I got the car expecting to have gearbox work done eventually, although I'd have liked a bit of time to enjoy things before it did.

My question is; where abouts these days do I go for an uprated TCU? Level 10 and IPT are probably out of the question for now due to being in the states. There was mention of one place in Germany but not sure if that is still going, waiting to hear back. The TC has got the viper mod I believe as well, I'm not sure if that will make a difference in replacing it, I'd like to keep the mod.

I picked my daughter up from school in it today as a surprise, she would have been too young to really remember me driving it before covid. Even taking it easy we were both laughing the whole way home. Its getting fixed no matter what!

Ultimately if it takes ages or is a massive headache I'll go with a stock/refurbed unit just to get it back on the road, I would appreciate some recommendations where to get that done as well.

Cheers,

J

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simonmcc
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Re: Torque Converter finally gave up.

Post by simonmcc » Thu Sep 11, 2025 10:03 pm

I think MRC in the UK still do the TCU stuff, they certainly reset mine back stock after I had to get the engine put back to stock too. That would have been about 3y ago though. All done through the post.
Fun: 2004 RS6+ Avant, Daytona Grey, Bilstein B14, Milltek.
~Fun: 2016 A6 Avant S-Line, Daytona Grey, fake-Black Edition (dechromed)
~Fun: 2019 A4 Avant 30 TFSI Black Edition

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Jayjay101
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Re: Torque Converter finally gave up.

Post by Jayjay101 » Thu Sep 11, 2025 10:08 pm

Cunningstunt wrote:Hello all!

Long time lurker. Bought my saloon off here in 2017, I think I'm its 3rd owner off the forum actually. I've loved every second of owning it, was my daily driver until covid hit. Since then its been sat in my garage on a trickle charger(Always something else needing money). Finally got around to getting her out and on the road. Fired up first time (followed advice on the faq) with no issues.

Its been at the mechanics getting everything I could think of done to it over the summer, and of course on the way back from the MOT centre (passed) last week it decides to start slipping in 3rd around 3000-4000 rpm. Flushed the gearbox oil a few more times to see if it would help but it then threw up fault code P0741-Torque converter lock mechanical failure. Oil seal in the TC perished over time? Not surprised it happened, I got the car expecting to have gearbox work done eventually, although I'd have liked a bit of time to enjoy things before it did.

My question is; where abouts these days do I go for an uprated TCU? Level 10 and IPT are probably out of the question for now due to being in the states. There was mention of one place in Germany but not sure if that is still going, waiting to hear back. The TC has got the viper mod I believe as well, I'm not sure if that will make a difference in replacing it, I'd like to keep the mod.

I picked my daughter up from school in it today as a surprise, she would have been too young to really remember me driving it before covid. Even taking it easy we were both laughing the whole way home. Its getting fixed no matter what!

Ultimately if it takes ages or is a massive headache I'll go with a stock/refurbed unit just to get it back on the road, I would appreciate some recommendations where to get that done as well.

Cheers,

J

rs.jpg
Germany is your best bet mate,that’s where i got mine done there’s quite a few places over there that will do it you have just got to find them


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c5 rs6 owner thats been known to cut the wrong wire.............

Cunningstunt
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Re: Torque Converter finally gave up.

Post by Cunningstunt » Fri Sep 12, 2025 7:51 pm

Thanks for the replies. I've sent off a few inquiries to places in Germany, will see what comes back.

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Shoppinit
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Re: Torque Converter finally gave up.

Post by Shoppinit » Sat Sep 13, 2025 8:29 am

Worth asking Topman. He's got his finger on the pulse more than most.
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."

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Shoppinit
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Re: Torque Converter finally gave up.

Post by Shoppinit » Sat Sep 13, 2025 11:49 am

Before you decide to replace the torque converter, you should use the Vagcom to make sure that's what the issue is.

You need to log the input speed and output speed in different gears to see if it's the TC slipping when its supposed to be locked or if it's the gearbox that's slipping.

I wouldn't discount the American suppliers. At least get a price.

The viper TCU mod is for the control unit. Nothing to do with any hardware.

Also make sure that you don't have the wrong filter installed (you put a new one in, right?) with the pick-up pipe too long. And are you sure you did the level correctly?
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."

Cunningstunt
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Re: Torque Converter finally gave up.

Post by Cunningstunt » Sat Sep 13, 2025 7:48 pm

Lots of helpful stuff and things to check, thanks very much.

Cunningstunt
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Re: Torque Converter finally gave up.

Post by Cunningstunt » Thu Oct 16, 2025 2:06 pm

Hello all.

Next question; while the gearbox is out of the car is there anything worth doing on the back of the engine while its out?

Cheers,

J

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Shoppinit
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Re: Torque Converter finally gave up.

Post by Shoppinit » Fri Oct 17, 2025 8:26 am

Possibly the crank oil seal. You might want to replace the EGT and lambda sensors while they are accessible.

Did you remove the engine and box or is the engine still in the car?

There used to be a lot of threads on what to do while the box was out. Might be worth a search back through the forum.
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."

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