BMW dealers usually don't do much in the way of transmission diagnosis, and very little in the way of repairs. They don't have the parts, they don't have the tooling, and they don't have the training. BMW offers their dealers exchange transmissions, so that is likely to be a dealer recommendation.

Take it to an independent shop familiar with your model of transmission. If a shop did it a year ago, you need to decide if you are going back to the same one or trying another. What was the warranty from the overhaul a year ago? Was it overhauled, or just repaired?

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue