The Dual Clutch Transmission (DCT) found in the E9x M3 range is a work of art. Super smooth and super quick. On the whole, the gearbox is very reliable. Unfortunately, a reasonably common fault is oil leakage from the mechatronics cover as well as the oil pan gasket.
Eventually, if the oil leak is left unattended, gear change faults may occur, illuminating the transmission warning light and maybe even a loss of gear selection resulting in a breakdown situation.
The gearbox requires removal to allow the replacement of the side cover. It’s always a good idea to change the oil and filter at the same time.
Once the oil pan and cover are replaced, the oil is then renewed and the oil level checked and adjusted using BMW diagnostic software.
All clean, leak free and as good as new.