torque converter lock up

When the torque converter clutch (TCC) locks you can feel a slight surge and then you will see the tachometer and speedometer tracking each other precisely rather than the "fluid" relationship between the speedo and tach when the TCC is not locked. TCC lockup is like when you have the clutch engaged rather than slipping in a manual transmission car. Usually the TCC only locks up in high gear and with the engine warmed up, at a steady throttle. If you let up or push down on the throttle pedal, the TCC should unlock at that time. if you have any transmission malfunction, the TCC probably won't lock up.