Quote Originally Posted by buddrow View Post
4L80E is based on the TH400 with an over-running clutch, an overdrive clutch, and an overdrive gearset added. It is beefier and bulkier than the 4L60E, requires a TH400 style driveshaft yoke, and slightly different shift solenoid operation than the 4L60E.
The 4L60E is i deed based on the TH700R4 with electronic controls added.
actually, if you lay the planets for both of those side by side, you will find that the 700/4l60 planets have physically bigger gears --- but the apply components for the 400/4l80 are bigger ---- plus the 4l80e does have the EXTRA planet in front for overdrive as stated above, so it doesn't mind if you tow in overdrive. The 700/4l60 uses the rear planet for overdrive, and if overloaded, will overheat and turn pretty colors of blue/purple/black as they are melting away......