This entry documents the various failure points of the DCT transmission using my original "DCT-001" in the V8 M3. It was leaking from everywhere."
The DCT is awesome, but it isn't perfect.
The DCT transmission is a marvel of engineering and remains to this day the best automated transmission BMW M ever fitted to a car. The ZF lacks the visceral nature of the DCT, and SMG owners need to take a pause and be rational about what we got with the S54 and S85.
The DCT transmission are notoriously known for being designed as Lifetime Fluid by BMW M. That may very well be accurate for street use and under normal use.
Unfortunately for us, BMW didn't expect its DCT transmissions to leak as we now know today. This is further reflected in BMW's own notes on its Technical Service Bulletin on the DCT.
"This BMW DCTF-1 Pentosin fluid does not require regular service maintenance. It is an extended life type of fluid and should not be replaced.
The proper fluid can be obtained using part number 83 22 0 440 214 (1 liter container) or 83 22 2 147 477 (20 liter container). The vehicle requires approximately 9 liters of fluid."
The failure points.
Fortunately for us, we have permanent fixes to most of the DCT leaking issues and access to much more affordable DCT compatible fluids. Back in November 2021, I started noticing my E92 M3 DCT transmission was leaking from all over the place.
I was planning to install the S65 DCT Lightweight Flywheel. As it requires the transmission to be dropped, I decided to combine with a complete DCT service. It came out to be an expensive while you're in there maintenance.
I say sort of as I was initially expected only the main pans to be a leaking problem, but there was more to it.
It was leaking from everywhere: top, side & bottom.
1. The mechatronic' o-ring.
You can see the accumulation of oil and dirt at the top of the transmission.
2. The side pan.
My side pan gasket was leaking towards the bottom corner sections.
The side pans covers the electronics of the DCT which bath in transmission fluid.
3. The main pan.
The S65 and S85 and both riddled with such cost cutting measures: throttle actuators, VANOS covers, coolant bleeder screw, power steering fluid covers, etc. This is yet another case of BMW using plastic where it shouldn't have. The most obvious culprit was also leaking on my transmission.
The plastic pan warps, causing distortions in the gasket's channel. Changing out the gasket alone is not sufficient.
The main pan is where most of the transmission fluid is held. Once it starts leaking here, it drains relatively faster than other failure points.
Up next: I list the SKUs, and document the servicing process of my original DCT.