I'm working on a 99 Ford F350 Super Duty, 7.3 for a buddy of mine. We're servicing his differentials and doing a cooling system exchange this weekend. As normal, I'm doing my research prior to tackling this job. My preliminary research determined that he "should have" a Dana 60 up front and Dana 80 in the rear. Well, this morning I went down to his house to take photos of the rear end covers and oil type tags (couldn't get to the ID tags on the ground).

Looks like he has a Sterling 10.25" differential. The cover is a 12 bolt cover vs the 10 bolt cover from a Dana 80. The front is in fact a Dana 60. According to the guys over at dieselhub.com, the Sterling 10.25" axle was installed from 85-92 (1st gen) and 93-97 (second gen). One would think that my friends 99 would have been upgraded to the Dana 80 at the assembly plant.

This isn't a complaint per say, I am just wondering what might have happened and be able to help my buddy down the road with any issues that may arise when ordering parts.

Does anyone have any interesting history on what I'm seeing with this setup?

Thanks.