The handful of parts that are physically interchangeable between plastisol and permatuff minus the water valve, door latch, upper rack guide, and screws; had engineering, design or build modifications done to them. Such as the pump bodies being re-shaped to have less carry over water, the pop-up tower water distribution slots changed, number of wash arm holes consolidated, drain solenoid encapsulation and drain bracket design changed, lower rack wheels, ect. Beyond these changes the rest was a totally new design.
Just about every single part was re-examined, reconsidered, recalculated, re-tested and modified as needed to fulfill GE's new goals. Some engineering changes were relatively minor like the spray arm hub, while others were a completely new design like the permatuff tub and door, detergent cams, detergent cups, vent system, heater, timer, sump boot, sump grates, fascia molding, door hinges, motor mount, float, wire harness, cycle sequence, and the list goes on.
Just because a handful of parts are interchangeable between permatuff and plastisol, doesn't mean they have not been re-engineered in some way. In fact the same pump and motor assembly between 1967 and 2007 has probably endured at least four dozen engineering revisions everywhere from the motor bearings to the size of the drain port to the macerator to the seals to the motor's protector to the drain flapper, ect despite the fact said pumps are physically interchangeable between so many models.
GE dishwashers peaked between 1983 and 1991. After that the decline began.
