The 4T65E/4T65E-HD has a common problem where the valve body wears out and does not allow the shift pressures to build up quick enough. The PCM senses this, flags the P1811 P0741 trouble and "corrects" the problem by increasing the pressures and shifting to be extremely quick. The transmission will slam the shifts until the car is turned off. The problem normally occurs when the temperature is warm/hot and the transmission shifts are slower. The P1811 P0741 trouble does not illuminate the MIL light but the PCM will retain the code. The usual fix is to install a shift kit like this.
