For 1990-2009 cars

The Hydra-Matic 4L30-E uses a line pressure control system which has the ability to adapt the system line pressure in order to compensate for normal wear of clutch fiber plates, seals, springs, etc. The adapt feature is similar in function to fuel control (integrator/block learn).

The Hydra-Matic 4L30-E transmission uses the adapt function only for the 1-2 upshift. The TCM monitors the engine speed in order to determine if the shift is occurring too fast (harsh) or too slow (soft) and adjusts the pressure control solenoid in order to maintain the correct shift feel. The line pressure can adapt to values ranging from 5 psi below, to 10 psi above the normal line pressure.