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2,793 Posts
Thanks Brobb :D, I can't see why I couldn't ever ship one to you.

The best thing I can do at the moment is let any of our fellow Perth Touareg owners see what it's like in my car to build some third party feedback, the difference really is night and day.
Improve i am very interested in a setup if possible ?
I presume a MY12 would still accept as the transmission is still the same ?

cheers Drag

2,793 Posts
Hey Improve (and others.)
I did PM you about the module and thanks for returning my PM very much appreciated.
What you have done with the lock up converter lockup is great and clearly what people have been wanting without knowing(y)
I have a question and one problem to relay, but am really only asking for an answer for the question (but if anybody wants to comment to the problem feel free.)
Scenario My 2013 7P (rocking horse poo model, 4xMotion, rear diff lock, area view camera, aircon seats as well as heated and memory function, 4 zone aircon with a bluefin ECU tune including EGR delete claimed 220kw, that maybe a bit of a reach but made quite a marked difference馃檪 )
I purchased at 150,000kms now at 210,000kms.
The previous owner who i never met towed a horse float, not sure how big or how much towing but i think quite regularly used to tow.
The car is used as my wifes daily driver and our caravan tow vehicle.
I have done i would say upwards of 15,000kms + towing our loaded 2.6t van with 3 passengers in the car.
I have let the vehicle decide what gear to be in most of the time during towing and that has worked with no issues.
Some times i may run in manual mode and preempt a down change for an upcoming hill.

Now the question and issue if you are still with me馃槒
Last trip in the final 600 to 800kms on the return leg i am getting a fault with the transmission listed as P0741 torque converter clutch stuck off no power being transferred.
This doesn't happen instantly upon towing but will happen every time during towing the van at some time and keeps repeating this fault even when cleared.
To me it is clearly load related as it really happens most times at the start of a climb up a rise.
At no time does this fault happen when the car is not towing the van.
Also i have towed an empty car trailer (700kg) then loaded a box weighing 700kg (1400kg total) and towed this with no issue at all.
I believe it is either a worn clutch in the torque converter allowing slip or an internal solenoid fault in the transmission and the speed sensors are picking up differences.
This may have been caused by a lot of towing over the cars life, and maybe towing in 8th gear with a big load on behind which a lot of people with various cars over the years have advised against towing in top gear.:unsure:.
Any way when it faults out during towing the van the transmission still shifts between all gears just the lock up clutch doesn't work and revs are up at about 2,800 when towing at 100kph and the tranny feels very spongy due to converter slippage and of course you see an increase in trans fluid temp.

Hope you all are still with me.

I am pretty sure it is the torque converter is causing this and to cover any possible transmission related issues causing this i have obtained a low mileage Q7 transmission and torque converter from a wrecker. (VW wanted $5,500 for a new converter and wreckers wont sell a torque converter separate from a transmission)
The donor Q7 also had no tow bar fitted.
By the way all the Q7 part numbers matched my Touareg exactly down to the transmission code so happy days.(y)

When i replace the Torque converter and transmission it will also give me the chance to find and rectify to very common oil leak at the bellhousing to block area found in Touaregs.

This brings me to the question i want to ask.
Would it be possible to program/install an inhibitor with an on off switch to prevent change up to 8th gear when in full auto mode ?

I know this is maybe a stretch but is linked somewhat to what improve has already done

Thanks for reading my long winded story, i hope for possible feedback.


2,793 Posts
My thoughts to the problem first with plenty of questions.

When it faults and you are going up the incline, what speed and what gear is it in? Can happen in any gear from 5th up to 8th, happens when in sports mode, also happens in manual mode. How far into the journey are you? Have seen it happen early in the trip of a morning after an overnight stay, but does seem more often when the transmission is fully warmed and has done a bit of driving. Do you happen to know the transmission temp (if its logged on VCDS along with the P0741 code information) Trans fluid temp is not high at time of fault but can clearly see the temp rise after lockup clutch stops engaging.
When you say you clear the fault and it returns immediately. It doesn't usually return immediately after stopping and fault clearing but will always return maybe 30km down the road more or less sometimes. When you stop and cycle the key on and off it resets the fault until the 3rd time then it sets a hard fault. This requires VCDS reset. Can you feel the TC locking up at all when first taking off in D3 and taller gears? Yes transmission operates perfectly before fault. even when driving on the flat? or is it doing exact what you say and the fault occurs immediately and can feel complete loss of TC lock up? As soon as the fault occurs the lockup clutch no longer works in any gear and cruise control cuts out and when you stop the engine is idling at about 1000rpm till you reset it by cycling off the key.

What happens if the car was left the rest over night? I'm assuming the TC lock up holds again as per normal until some point again during your journey? Yes how far into the journey does it take for it to fault again, or does the literally happen as soon as you hit the first incline only? As i said is a bit random but in my feel it is load related as to throttle position eg more for climbing up a hill seems to be consistent in causing the fault as it rarely happen on a long flat road.

Depending on the answer's, if it somewhat intermittent I would be leaning towards replacing the N443 lock up solenoid and cartridge first along with a transmission filter/flush. Transmission had a full flush, filter screen and new Ravenol fluid (RAVENOL ATF T-WS Lifetime) about 20,000kms ago. Yea looked at that N443 but the solenoids are not the easiest to get hold of or are Chinese versions also try DQ500, 0BT, 0BH (DSG 7 with wet clutch) ( so the low kilometer used tranny i have take will care of this potential issue and the torque converter if it is that. As i said this will also allow me to hopefully repair my rear oil leak. It seems from what you are describing IMO that during your journey enough heat is eventually being generated naturally that the N443 Modulation valve is no holding its position like it should, allowing the TC to slip. More heat is generated as we know when towing so that might explain why it only happens when towing your van and then eventually the incline is the breaking point.

As you rightly mentioned, the TCM is recognizing the slip by measuring the trans input shaft speed compared to engine speed and since its no longer a close match like it should be when the TC is commanded to lock, it flags P0741. (must only be looking at greater speed and taller gears? otherwise I would have come across this during my testing when stopping D3 lock up, and I also trialed stopping lock up in D3 + D4 with no P0741 detected)

Once P0741 is flagged, the TC is no longer locking up at all in any gear, which isn't ideal for the transmission if you are still driving for extended periods.
That's not to say the TC isn't at fault here, but I know what I would be doing first.

Now to your question, by far the easiest solution is to manually use the gears and hold it back to the position most suitable at the time. Yes this is certainly the easiest method, but being used to auto it is easy to forget after some time that you have the transmission in manual mode, and next you are loading and stopping a down change at the base of a hill. Best for others to chime in here to see what they do towing there loaded vans. Are most driving in D mode the whole time and then manually shifting back when approaching inclines or plenty of head wind? Are you comfortable having the transmission stay in D8 whilst towing? Yes that is a good thing others could chime in with! (y)

But, yes it's probably possible to have D7 selected as the tallest gear when driving in D mode only and could be operated by a switch also so it only restricts D8 when you want it to, eg when towing only. I would only explore this if you really cannot restrict top gear comfortably yourself by using the gear shifter, or potentially a TCM remap could be done so its more reluctant to upshift to D8 when there is more load. That would be my first preference.

Otherwise to do what you are asking, would need D8 solenoid wires running though some relays, so whenever the module is switched ON to restrict top gear and whenever D8 bus message is received, it will then send D8's pwm signal from the TCM back to D7 solenoid, instead of D8. This should keep D7 locked in gear without feeling any change. Mind you it will still display D8 on the dash. Plenty of "safe" testing would need to be done here with some failsafe devices built in, as at no point do you want 2 gears being accidently selected at the same time.
Yea i was hopeful of and easy yes, but realized that was not probably likely so

PS. Even when i change the transmission i will open up the sump to see if i can view any clutch material inside the strainer or magnets as all this was cleaned when the service was done.

Thanks for your reply

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