That does sound like torque converter. I think it's well covered issue when you do search. I believe there is a company who rebuilds them. I've seen them advertise in Bimmer magazine. I'm sure google search will yield plenty.

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2010 BMW M6 * Black Saphire Metallic * Full Black Merino Leather
2019 BMW X3 M40i * Alpine White * Mocha Leather