Hi folks, Even though this is an old post, it has helped tremendously with my DCT fluid kerfuffle by my indy workshop last week.
My transmission oil pan had a bit of a leak/weep common to our DCT so I decided to change the pan and replace the trans oil. The trouble that followed could have been a costly one had it not been caught early.
Draining the oil and replacing the pan was simple enough but refilling the transmission oil proved to be a bit more tricky. Because there's no electronic oil level sensor or dipstick, it was pretty much a guess work filling the oil until it was overflowing.
Well, it started overflowing at 6.5 liters and the mechanic felt it was full and stopped there. He didn't follow the multiple procedure as the above OP post nor did he use the DIS to perform the oil calibration steps.
Driving home that day was fine, shifts felt smoother and the judder from 1st gear was gone. Great, I'm thinking. The next morning, I started the car and pulled out but the transmission felt like it was slipping. Half a block down the road, the car stalled and the DCT shifted into Neutral by itself. We managed to limp back home and then the car stalled again and this time it wouldn't start.
Reading the OP post, it indicated that the DCT capacity is 9.5 liters so 6.5 liters refilled the day before seemed a bit off. This insufficient oil could have damaged my transmission in a costly way. The workshop filled another 1.5 liters and all seemed ok.
The next day, car drove normally but had a bit of rough gear shift. It then got worse and the car stalled but did start again so managed to get it to another Bmw specialist workshop.
This time, the oil level was checked and the refill procedure was followed using the DIS oil calibration steps and DCT is working fine again.
Moral of the story is that when Bmw says the transmission/DCT oil is lifetime, they mean don't touch it!
My car has about 35k KM and the original factory oil was clear and the filter was clean when it was removed. Unless you have a bad leak from the pan, do not change the "lifetime" transmission oil. And if you have to, take it to a reliable Bmw dealer or a competent workshop to get it done.
Cheers, Howie