Are you guys with the 4th gear program saying that your programming only invokes 4th gear ("4" shows up on the "target" side of the trans keypad), and the trans does not shift down past 4th? Maybe I'm confused. I had mine reprogrammed to invoke 2nd gear ("2" appears in the target window). The trans then shifts, within RPM limits all the way down to 2nd gear as the coach slows down. The PacBrake stays on until about 6 or 7 MPH, so I rarely have to touch the service brakes until the final few feet. The trans never goes straight from 6th to 4th, but goes down throught the gears in order. The 5th to 4th change can be a bit "urgent", though, if slowing down quickly.
The only thing I would do to improve the way the Pac Brake works would be to install the system that allows the coach to coast in whatever gear you are in and does not engage the Pac Brake until you touch the service brake treadle and turn on the brake lights momentarily.
Just wondering what you all have for a shift program.
Andy