What is the difference between a 4R55E and a 5R55E transmission?

4R55E-4 SPEED AUTOMATIC TRANS. 5R55E-5 SPEED AUTOMATIC TRANS. The difference is in the shift strategy that results in 5 speeds, most of the internal components are the same for both gearboxes. Valve bodies are different. Both are electronic, and both were installed primarily behind 4.0 liter 6-cyl engines, 5r55e is an improvement over the 4r44e which in turn owes its legacy to the c3/ a4ld of yesteryear.