DCT skipping gears; air in the system?

[Route 16]

I've had the GTS transmission flash for like 2 years in the states. Prior to getting the DCT gasket replaced, sump filter, drain and fill. I had no issues with the transmission at all. Felt solid and didn't feel like a clunk (no issues with the driveshaft at all). It only happens driving on neighborhood speed limits and happens when I decelerate when I coast or stop and when I do accelerate I do not in gently because once it goes from 3 to 4 it feels jerky. Even reverse if it isn't warmed up, jerky. So skipping gears it's gone to 1st, 3rd, 5th, 7th and it won't go to 2nd, 4th, 6th. Once I turn off the vehicle and turn it back on. It's all good. The other day it went from decelerate to a stop (one way traffic) when I accelerated it went from 1st to 5th.

I mentioned the symptoms to a BMW shop while I'm here in Germany. He'll read the transmission codes but said it could be air in the system and he'll check the pressures. Is he right or pulling my leg? I would probably want to do another drain and fill, reset adaptations then GTS reflash?

[nycplumber]

Sounds like you're low on fluid. When you brake hard the fluid gets pushed to the front and the sensor won't let you get the next gear. That's why a lot of people upgrade to the slon dct pan. I would get more put in and have them add extra like is done in the GTS.

[Route 16]

Originally Posted by nycplumber

Sounds like you're low on fluid. When you brake hard the fluid gets pushed to the front and the sensor won't let you get the next gear. That's why a lot of people upgrade to the slon dct pan. I would get more put in and have them add extra like is done in the GTS.

This is true. I think I supplied 9L? The initial job and then maybe 1k miles later that's when it skipped gears. 2-3k miles later, I had a shop fill in more. But it's been maybe 500 miles later it skips again. Probably just drain and fill the whole thing over again? And purge it of air?

[M3SQRD]

Originally Posted by Route 16

This is true. I think I supplied 9L? The initial job and then maybe 1k miles later that's when it skipped gears. 2-3k miles later, I had a shop fill in more. But it's been maybe 500 miles later it skips again. Probably just drain and fill the whole thing over again? And purge it of air?

You can’t get 9 L into the Slon DCT (deep) pan + do88 DCT cooler (3x4 times the size of the stock cooler) . If you got 9 L into the stock DCT setup then you’ve overfilled the DCT.

[Route 16]

Originally Posted by M3SQRD

You can’t get 9 L into the Slon DCT (deep) pan + do88 DCT cooler (3x4 times the size of the stock cooler) . If you got 9 L into the stock DCT setup then you’ve overfilled the DCT.

9L was my guess since I was thinking of motor oil fill. But I gave 5L to fill then had another shop fill in more. How much though is what I'm unsure of since I was overseas when my brother brought in the car for me. But looking at the manual, the initial fill should be 7.8L?

Next course of action sounds like do another drain and fill?

[M3SQRD]

Originally Posted by Route 16

9L was my guess since I was thinking of motor oil fill. But I gave 5L to fill then had another shop fill in more. How much though is what I'm unsure of since I was overseas when my brother brought in the car for me. But looking at the manual, the initial fill should be 7.8L?

Next course of action sounds like do another drain and fill?

If you’re only draining from the transmission (i.e., not removing/replacing the DCT cooler) then you’ll leave around ~3 L in the system (lines, cooler, etc.). So you typically need only 5 L when changing the fluid in the DCT (companies that sell DCT fluid replacement kits included 5 L of fluid in their kits). Some people will perform a 2nd “flush” after a short time period to try and remove the rest of the old fluid that’s left in the system.