I use Mobil1's Synthetic ATF in my diesel and I had the filter replaced and the torque converter drained (make sure you do that). The car shifted really smooth afterwards but now it's back to "you can feel the shift" kinda shifting.

don't overfill the transmission. The transmission has to be at operating temp before you start measuring the ATF level.

I wouldn't flush the engine either. Just change the oil (let most of it drain overnight)

flush the brake fluid definitely! Use ATE DOT4 brake fluid (try fastlane)

power steering - most people would say MB fluid but ATF is also fine I think.

flush the coolant too. use mb anti-freeze (again just from hearsay) and make sure the ratio is correct and that u drain the block too.

good luck!

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2008 BMW 335i Coupe