Transmission hesitating or slipping

To fix GMC's transmission slipping or hesitating issue, first of all you have to ensure the fluid level is at the recommended level. Check the fluid's color and consistency; if it's dark or dirty, replace it. Flush the transmission system to remove debris and contaminants. Refill with the recommended type and amount of transmission fluid.

If the issue persists after trying the above steps, it may be necessary to rebuild or replace the transmission.