After an engine stop, the fan of cooling of a radiator can continue to work (up to 10 minutes). It can also unexpectedly begin to rotate even at the switched-off ignition again.
If the fan of cooling of a radiator does not turn on at strong temperature increase of cooling liquid, check a safety lock and replace it if it is necessary.
Speed of rotation of the fan of cooling of a radiator does not depend on the speed of rotation of the engine therefore extent of cooling cannot be raised having switched to lower transfer.
While the engine works evenly and at the movement under a hill speed does not decrease considerably, there is no need to include lower transfer.