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Owner's Manual - BMW North America, if it's an automatic...
Automatic and sport automatic transmission
Before towing, manually release the transmission lock, even if there is no malfunction in the transmission. Otherwise there is a risk that the transmission lock will automatically be engaged during towing.
Manually unlocking and locking transmission lock, refer to page 65.
Do not exceed a towing speed of 45 mph/70 km/h and a towing distance of 90 miles/150 km, otherwise the automatic transmission may be damaged.