When Ford started separating all of their transmission coolers, and making them completely independent of engine cooling, they added thermostatic bypasses to them. Depending on the platform, they can be within the cooler, inside the transmission, or in a block in between. As an example, ALL '98-up Panther platform cars (Crown Vic, Grand Marquis, Town Car) had a separate cooler with a 180°F thermostat and a bypass within the cooler. The same cooler assembly also housed the power steering cooling circuit.

The went to the added expense of the thermostatic control both for cold weather drivability and for transmission longevity.

At any rate, they are great coolers, and there are a gazillion of them in junkyards everywhere.