The recently discontinued Cherokee had a 4 liter in-line 6 and 4sp
auto.
The Wrangler also has the 4L6, but only a 3 speed auto.
Why put the inferior tranny on the QUINTESSENTIAL Jeep?
Four-speed automatics are less sophisticated than three-speeds, but not necessarily inferior.
Plus for the four-speeds: fourth is an overdrive gear, resulting in better gas mileage and somewhat less engine wear at highway speeds.
Plus for the three-speeds: they tend to be very sturdy, well-proven designs, and are less expensive to repair.