When pulling a trailer, Nissan recommends turning OD off.

Automatic transmissions have torque convertors, which bolt to flex-plates and then to the crankshaft. There is not an air-cooled clutch in the bellhousing like on a manual transmission.

If you were only doing 55 or 60, the transmission probably shifted into 2nd gear. Most automatics are geared so that 2nd gear at redline can take you 70+ mph.