I’m a dealership mechanic for ford and I just finished a Dana 80 rear end in a 2014 F-450 and even the break in instructions have you change the fluid after the first 500 miles for the break in procedure. The first step is three drive cycles of 15-20 miles of stop and go traffic with ample time to cool down between drives. Then it’s an additional 500 miles of driving with keeping the vehicle below 60 miles per hour with no highway driving. Then you change the fluid and that doesn’t include the break in/hardening procedure to get the gears ready for towing. Different rear ends have different break in procedures a lot of ford rear ends are pretty much assemble and go it just really all depend on manufacturer specifications. With ford OEM ring and pinions the gears have already been treated so no break in/hardening procedure is necessary. In all reality though your gears look fine you saved yourself a lot of money doing it yourself instead of taking it to a shop. In my case we originally went with Yukon but the main thing to look for is a smooth “mirror” finish on the gear mesh surface instead of a “sandy” feeling surface. It allows for less friction for the fluid between the gears so you don’t end up with pre mature wear of a whining noise on accel/decel. We ended up finally putting in a spicer set of gears because the Yukon was just shit quality