I was driving up a long fairly steep (6% grade) hill at about 120kph/70mph in cruise control. When the transmission downshifted out of OD you could first hear the torque converter unlock and then about 5 to 10 seconds later, the transmission would downshift, but when it did, the motor would rev about 500 rpm over for about 1/2 a second and then find the lower gear. Is this normal or does sound like transmission slippage and an omen of a big transmission fix-it bill?

 

Grab your wallet. It's time.

Steve

 

The rising then lowering of RPM after the shift could be the torque converter relocking, which is what it is supposed to do.