MR. N said:
In 1977.5 Ford’s new F250 axle now started to appear. Previously, the F250 ran a standard rotation closed knuckle axle (see reference pictures below.) This axle for the F250 44RS is slightly different than the F100 & F150 offered in 1977. The F250 is a little wider than the F100 & F150, for the wider 8 wheel bolt hub. The F250 also has 3" wide axle tubes with ½” thick tube walls, and the axle has many different small changes from the F100 & F150 to include larger brakes. This axle stayed this way until it changed to the Twin Traction Beam (TTB) IFS system of the 1980 model year.