A feature designed to improve fuel economy has been included in the automatic transmission on your vehicle.

A clutch within the torque converter engages automatically at calibrated speeds. This may result in a slightly different feeling or response during normal operation in the upper gears. When the vehicle speed drops or during some accelerations, the clutch automatically disengages.

NOTE:
The torque converter clutch will not engage until the transmission fluid and engine coolant are warm [usually after 1 to 3 miles (1.6 to 4.8 km) of driving].

This is normal. Shifting between the DRIVE and 3 ranges, when the transmission is sufficiently warm, will demonstrate that the transmission is able to shift into and out of Overdrive.