Were Heavyweights still in use when F-3s came on the scene?

I never understood the A-1-A arrangement. It's just leaving tractive effort on the floor.

The A1A truck had lower axle loads, which was important in the 1930s.  An A1A-A1A diesel could go anywhere a light Pacific could go with more power and more availability.

C-C (six axle) passenger units worked well when the track was maintained properly.

@rplst8 posted:

I never understood the A-1-A arrangement. It's just leaving tractive effort on the floor.

That EMC/EMD A-1-A truck was purposely designed for a VERY smooth ride at high speeds, over 100 MPH. It was designed for passenger service and NOT "high tractive" freight service. When the EMC/EMD FT was being designed in 1937/1938 the two-axle "Blomberg" truck was designed, having 40" diameter wheels.