Why is that? Cheap parts, or is it easy to do? Both?
Is cheap parts due to high demand? I realize that's a jab at GM but it has to be asked.
I know GM did tend to use the same design for years and years, so that helps drive costs down. When it's the same widget used for a long time, its easier to support on the parts side of things. As much as I dislike the 4L60 it sure did have a long run, as did SBC's.
Mostly due to the long run, The TH400 was in production from 1965 to 1993 with no major design changes, The 700R4/4L60/4L60E ran a little longer (1982-2013) but there were several major updates along the way.
Yes....Demand is there partly because 4L60E's need a little more attention than other units, But there's also all the LSx engine swaps going on, GM trucks being VERY popular, And Corvette, Camaro, & GTO guys tearing them up.
Why do you dislike the 4L60E? They sure are a versatile & efficient unit....Once you change the ratio's to 2.84, 1.55, 1.00, 0.70 from 3.06, 1.63, 1.00, 0.70, They really shine! It also takes some loading off the Dynamic frictions in the unit (2-4 band & 3-4 clutch).
However was able to design a 4 speed unit that only uses 2 Dynamic friction members & 2 Planetary Carriers was a very talented engineer.....Though it might have been a whole team of engineers??
Most other 4 speed auto's need 3 Dynamic Friction member & 3 Planetary Carrier......4L80E, 200-4R, & 46RE are some examples.
The Ford 4R70W/AOD uses a single Ravigneaux planetary carrier which is basically 2 carriers built into one...But needs 4 Dynamic Friction members.