Looks like you need a Tech2 or similar aftermarket scan tool to do a relearn. Ensure your fluid level at 180-200°F is in the crosshatch area and that the correct fluid was used (Dexron VI). If it isn't that may be the cause of your shifting problems. Otherwise you can try this procedure.
Service Fast Learn Adapts
Service Fast Learn Adapts is a procedure for 6-speed automatic transmissions in which a series of tests are run to allow the transmission control module (TCM) to learn individual clutch characteristics. Once the clutch data is learned, Service Fast Learn Adapts translates it into the adaptive data cells, which the TCM uses for clutch control during shifts. The scan tool provides initiation of the Service Fast Learn Adapts procedure. This procedure is to be used following transmission repair.
The Service Fast Learn Adapts procedure must be performed when one of the following repairs have been made to the vehicle. Failure to perform the procedure after one of the following repairs may result in poor transmission performance, as well as transmission DTCs being set:
Transmission internal service/overhaul
Valve body repair or replacement
Control solenoid (w/body and TCM) valve assembly replacement
TCM software/calibration update
Any service in response to a shift quality concern
NOTE: Ensure the following conditions are met before performing the Service Fast Learn Adapts procedure:
Drive wheels are blocked
Parking brake is applied
Service brake is applied
Zero percent throttle and no external engine RPM control
Transmission fluid temperature (TFT) is between 70-115°C (158-239°F)
Transmission gear selector has been cycled from Park to Reverse 3 times in order to purge air from the reverse clutches.
Use the scan tool to navigate to Service Fast Learn Adapts by selecting the following commands:
F1: Transmission Control Module
F5: Module Setup
F0: Fast Learn Adapts Process
NOTE: If at any time during the procedure, required conditions are not met, Service Fast Learn Adapts may abort and the process may need to be started again from the beginning. If this occurs, the transmission will be left in a neutral state until the controller is shut down, key OFF and remove the Tech 2 and wait for more than 30 seconds prior to re-try procedure. If the procedure repeatedly fails, a limit that engineering set is being exceeded and there is possibly a transmission hardware issue.
Use the scan tool to perform the Service Fast Learn Adapts procedure. As the procedure is being performed, the scan tool data display will provide operator instructions. Follow the scan tool instructions as required.
Once the procedure is complete, shut OFF the engine and power down the TCM. You will lose communication to the scan tool.
Ensure you exit back to the main screen in the Tech 2, shut the Tech 2 OFF, and unplug it from the DLC or the controller will not shut down leaving the vehicle in a neutral state.
NOTE: When the Service Fast Learn Adapts procedure is completed, the transmission will remain in a neutral state until the controller shuts down. If after 1-2 minutes of sitting, with the key OFF and scan tool removed, the vehicle remains in a neutral state, disconnect the battery and wait 5-10 minutes and then hook the battery back up. Reverse and drive should return.
Restart the engine. This will complete the Service Fast Learn Adapts procedure.
If the Service Fast Learn Adapts will not run and the above stated conditions have been met, ensure the following:
TFT is between 70-115°C (158-239°F).
Brakes and brake switch are functioning properly.
No active DTCs.
Closed throttle and engine RPM increases above 1500 RPM while at entrance of the test.
Park/Neutral position switch is properly adjusted and functioning.
Line pressure control is able to provide 1000 kPa and is within specifications.
Vehicle is not moving, or vibrating excessively.
Clutches are properly assembled.