My honest experience after a year of ownership and 2000+ miles driven mostly local with 2 road trips equaling 800 miles is pretty positive. The are 2 ways to drive a bus with the T444E and AT545......
The first way is to floor the pedal and let the tranny RPM shift at 2600 RPM. This causes longer shift times and harsher engagement. This method works, but builds heat fast in the tranny. You might think you are taking off and building speed decently, but you actually are not. This may also cause driveline issues down the road.
The second and best way to drive this setup is to start off from a stop at half or just above half throttle. The tranny will shift through the gears much quicker and you will be in 4th pretty quick. Maintain the same half throttle until your speed increases to 45 MPH and then you can down the accelerator until you reach the desired speed.
My bus drives pretty good. Learning how to drive it and using the half throttle thing for take off has made me understand how the fluid drive tranny works. Once up to speed, this thing cruises at 55-60 mph comfortably on the flats. Hit a hill and it slows considerably, but still maintains 35 MPH after dropping to 3rd while climbing. I can haul at 65-70 MPH on a flat interstate, but at this speed the RPM's are approaching 2800 and racing the engine. This also builds heat in the tranny and cooling system after extended driving running high RPM's. I feel I could run the bus like this for many, many miles, but this might cause premature engine or tranny wear that can be avoided if I just cruise at 55- 60 MPH.
The 7.3L can be run over 3000 RPM like they do on the Ford Powerstroke applications. I feel the engine can run as hard as you want it to. I had my bus up to 75 MPH on a downhill mountain run and the engine was spinning hard at 3100 RPM (My road speed limiter and RPM limiter is disabled) but I had no fear that the engine was hurting in any way.
I have no fear of my T444E having a major mechanical issue. I only have fear of my transmission because of all the hate I read about the AT545 on these forums even though my transmission seems fine. I suppose if you want to run balls to the wall all the time on the interstates and want to keep up with traffic, then find another bus with a different setup. If you want to take the scenic route and enjoy the ride, then this setup will work for anyone.
John