The wife kept complaining the engine would rev when driving. I finally took it out and experienced the following. At around 45 mph with the trans in Drive, I observed the engine would bump around 500 rpm's very intermittently. Finally it rev'd up 1000 rpm's. I quickly shifted to the manual gate and observed it indicated the trans was in 2'nd gear. I bumped it up manually and shifted back into the Drive gate. After a few minutes it did it again and when I shifted over to the manual gate it indicated the trans was down to 3'rd gear. I shifted it manually to 4th and kept it in manual mode. It did not occur again. Does this trans have an electronic shift solenoid of some type? Need some help diagnosing the problem. I don't believe it is internal to the transmission and it does not seem to be slipping clutches or a blown torque converter.