DSG Faults - Mech Unit Repair - Read Me First

[rockstar143]

Hey all, figured I'd make a quick thread to share my experience with a B8.5 mech unit in my beloved S4...
Got the car back from a nice young man I sold it to with an occasional but pretty consistent trans fault.
"2nd Gear Selector" fault...would go limp mode on the trans and if you didn't turn the car off and back on
immediately it would trip the TPMS fault that won't clear until you go over about 45 mph.

I dove in to figure out how to fix it. Wiring kit seemed unlikely to solve the problem so I delved deeper.
Found a company online out of NY that sells you a mech unit that has been gone through. They use only
borg warner pressure switches and solenoids and oem wiring. Get this, price was $1050 with a $450 core
charge. Ummmm...that is including the $640 oem wiring kit "fix" that is sold by the big stores. They were
tenacious in handling troubleshooting with me, answering questions etc. I personally had a shipping mishap
that ran another $350 for a cloned TCU (working with UPS to rectify that). DO follow their instructions to remove
the 5 bolts and remove your TCU from the heavy mech unit for shipping. I should have but was unclear on that
initially.

In the end, we tried using my mech unit but I had the harsh drop to first that wouldn't go away. Ran the adaptations
and just wouldn't. They kept their word and shipped me ANOTHER mech unit (sans TCU) with a prepaid label to ship
my old one back. Problem seems solved and I'm in heaven, my car is shifting beautifully with no more errors.

An absolute dream company to work with and a lifesaver for anyone having mech unit issues.
These cars are fantastic and as much as I love my 6MT S5...there's a place in my heart for the smooth and fast shifting
DSG as well. Figured I would share my experience with the forums.

Feel free to reach out to me with any questions. In the end, I could have the mech unit out of my car in about 45 minutes
with very little mess. And everything back in and dialed in in about another hour and a half if I take my time. (I bought
a pneumatic fluid extractor/dispenser that changed my life...I'll link).

Cheers and happy motoring,
J.

https://www.amazon.com/gp/product/B0CQKZZ6WW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

https://mlreng.com/products/dl501-dsg-audi-s-tronic-0b5-mechatronics?variant=40520905293911

https://live.staticflickr.com/65535/54226641730_5168ed2c8e_k.jpg (https://flic.kr/p/2qBPHmN)

[Blackcoog]

I'm looking into doing this on my S6. I don't have any codes but I have a rough 1-2 shift from a stop, almost like it delays for a split second before engaging 2 and it has gotten worse over the past few years. It happens every time from a stop.

Also, it will randomly not shift 2-3 until I left off the gas. It will just rev up and I have to let off the gas slightly to allow it to shift. It happens maybe once or twice a week only when warm after about 10 miles of drive time. Wide open throttle it shifts perfect. They don't seem to line up with the common issues people have with the DSG.

I was going to order a kit replace the flex tape and other parts on the mech unit but this is a great deal for $1k plus core.

[Blackcoog]

Yesterday I ordered the mechatronic from: https://mlreng.com/products/dl501-ds...40520905293911

I emailed them the info on my car and my current issues and asked if they feel that the mechatronic would fix it. They called me this morning and gave a detailed explanation of what could be happening and that the mechatronic would fix it. They said I could ship them my mechatronic and they could diagnose it if I wanted but they are backed up at the moment so it would take a few weeks. I don't want my car down that long so they are shipping me a rebuilt unit and I'll try that. I'll report back what happens. So far my interaction with them has been great.

[Silence]

awesome. keep us updated - seems like a good vendor to work with on DSG issues.

[Blackcoog]

Mech unit received and I removed mine without any issues.

https://i.imgur.com/zr09pBz.jpg

Production date numbers decoded:
My Mechatronic: Q37D1034 = (2015, 37th week, D1 = Tuesday 1st shift build, 34th mech built that day)
MLReng Mechatronic: T05J1028 = (2018, 5th week, J1 = Thursday 1st shift build, 28th mech built that day)

I am down waiting on some of the plastic pipes and I should have ordered before hand. Here is the first group of pipes I had to order (0B5315105TA). They are supposed to be all one plastic piece and you can see one pipe missing because all 3 should be there. The other one was stuck in the trans. The plastic connecting them is brittle.
https://i.imgur.com/YUsJGsN.jpg

The part should look like this:
https://m.media-amazon.com/images/I/71TdjLP7PEL._AC_UF894,1000_QL80_.jpg

The other double tubes I removed from the trans side broke apart so I also ordered those (0B5315105TC). The part should look like this:
https://wolfautoparts.com/media/catalog/product/5/6/56bf18115f28e1e8c37c9d43cb01d414dbbdc3d963888fbaa9 e5cc57b5ace608.jpeg?store=default&image-type=image

Here is a picture of the trans from below with the mech removed. I already set the shift forks to neutral for the reinstall.
https://i.imgur.com/K0I4hGO.jpg

My only other concern is that when swapping the TCU there are 2 O-rings that go between the mech and the TCU. I would have liked to replace those but I can't find a part number. I think they are ok but I'd hate to have an issue due to leaky O-rings. I don't know if I can get any O-ring from the hardware store due to the temp/fluid.

[Blackcoog]

I picked up the tubes I needed an installed them into the trans. You can see the two long black pipes and the 3 short stubby ones installed here:
https://i.imgur.com/HTUyQnp.jpg

The mech unit went back in without too much trouble. I set the actuators to 32mm as required for my mech unit. I slide the unit into place and then verified all 4 forks went into the actuators. I tried to get some pictures of the forks going into the actuators and this was the best I could get.
https://i.imgur.com/ZBBZ8rr.jpg
https://i.imgur.com/aniwBVc.jpg

After everything was buttoned up I filled the pan with about 5 liters before it started coming out. I cycled through P, R, N, and D for about 30 seconds each. I pumped in another liter of fluid before it started coming out. Then I took it for a test drive to get the temp up to about 40C based on the VCDS transmission fluid temp reading. I then removed the plug and added a tiny bit more fluid and let the car sit flat to drain out any excess. Finally I reinstalled the plug and then went though the DSG adaptation process in VCDS (https://www.youtube.com/watch?v=2SL-6nbgSoI).

So far everything seems great but I need to get more miles on the car to be sure. It takes about 1-3 hours of driving for the car to finish the clutch adaptation process after running through the menus in VCDS.