Inspect the shift solenoid valve C function with the HDS.

Check for a seized shift solenoid valve, and inspect the O-rings.

Check for an incorrectly installed transmission, and check the drive plate for wear and damage. Replace the drive plate if it is worn or damaged.

Check the stall speed.

Check the line pressure.

Replace the torque converter.

Be careful not to damage the torque converter housing when replacing the main ball bearing. You may also damage the ATF pump when you torque down the main valve body. This will cause ATF pump seizure, use the proper tools.

Check the lock-up shift valve in the main valve body for free movement, and check the valve springs for wear and damage.