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MY17 Touareg Wolfsburg
126 Posts
Discussion Starter · #52 ·
Really keen to understand how much difference this will make to mine. No reason to suggest it would be any less than yours. Looks quite easy to install and turn on and off from what you've described (with the addition of a switch).

The wife doesn't like driving mine compared to her Tiguan Allspace due to the... "Huh? What? You want me to go? Now? OK - I will in a bit - when I'm ready..." response of the Treg. This could assist in improving that - especially around town.

Maybe see you at the WA catchup in a few weeks.

Nice work!

Hi Andrew, Unfortunately I won't be able to make the meet up on the 17th due to work commitments. Will wait and see if that still goes ahead as planned or if weather interrups that date. If it pushes to the following Sunday I'll be there.
But I'm happy to meet up some where too so you can try it out personally and will look to plan another meeting date so anyone else in Perth who is interested can get a feel.

It's funny you mention that. My wife much preferred driving our TDI Golf since the acceleration response was much more direct and predictable.
With the extra cylinders, power and torque the Touareg has (when not restricted) it should drive better. And it can.
Honestly there were times especially when turning and crossing multi lane intersections where the Touareg felt unpredictable with its acceleration response to pedal input, it was always in 3rd gear when the TC was in a locked state. I finally put those issues behind me now :)

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MY17 Touareg Wolfsburg
126 Posts
Discussion Starter · #54 ·
@improve Curious as to what's in your TC modifier? Raspberry Pi or similar to connect to the Canbus, read/interpret the comms packets for D2 to D3 upshifts, and then switch a relay to isolate the soleniod as required?
Yes, I summarised how it worked back in post #14. I've intercepted the TC solenoid wiring and it diverts the TC pwm signal through relays to a load resistor only when D3 is selected.

All the traffic is listened to on the powertrain bus, but filtering is set to only look for the ID, message and byte responsible for the actual gear selected.
When ever the message for D3 is received, that the trigger to close the relay.

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MY17 Touareg Wolfsburg
126 Posts
Discussion Starter · #56 ·
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🙂 )
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😏
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.

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? How far into the journey are you? Do you happen to know the transmission temp (if its logged on VCDS along with the P0741 code information)
When you say you clear the fault and it returns immediately. Can you feel the TC locking up at all when first taking off in D3 and taller gears? 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?

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? 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?

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. 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 recognising 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. 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?

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.

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MY17 Touareg Wolfsburg
126 Posts
Discussion Starter · #59 · (Edited)
Revision 2.0 is currently in progress, this time the throttle position sensor has been added into the code.

I've added this as I wanted to explore the effects of having the TC lock up, however only whilst during deceleration (foot off pedal whilst in D3) and is to maintain engine braking functionality whilst in D3.
I managed to get a short test drive in last night with it working, but I'll be away now until next week before I can test it a little further.

I may add a short duration delay, say 500 millisecond from when foot is off the throttle before it allows the TC to lock up during deceleration in D3.

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MY17 Touareg Wolfsburg
126 Posts
Discussion Starter · #61 · (Edited)
Just added a paddle shift wheel to my 7P after following the guide here: T3 Steering wheel paddle shifters

Used OBDELEVEN retrofit app to do the coding. All went well after a little extra time to release the airbag.
All works great.
Something odd though is the auto gear changes are much better, more aggressive and responsive without being edgy. Don’t know if the coding reset the gear shift learning or what but it’s great. It seems like the tourque converter unlocks now when in third and you floor it putting you in boost where as before it would just lug its way there.
Anyway thought I’d post for you guys incase any of that was of interest 😀
Nice work mate!
My wolfsburg has the paddle shifters, they are a nice feature making it quick and easy to flick it back a gear when you want/need, I bet you will be happy with them!

If you are noticing quite a change then I agree, it seems like a reset has occurred on the self learning adaptions somehow.

How much throttle do you need to apply before it's unlocking? Or is it only when you "floor it" , like you mentioned?

The TC controler has the benifit of applying or easing onto the converter stall as much as you desire. It makes it much more responsive and linear down low & mid range which is what I always wanted to address 🙂
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