Ranked by parasitic loss (lowest first):
Dana 60
Chrysler 8-3/4" (there are 3 pinion types)
Ford 9"
Pictured left to right in the 1st picture is Ford 9" 2.47, then Dana 44 2.72, then Dana Super 44 3.07....
These pics are not to discuss the parasitic loss directly, but for me to point out a few things I noticed and to ask a couple of questions:
The 2.72 standard Dana 44's splined portion is about 1/8" less OD than that of the Ford 9" 2.47. The Ford 9" 2.47 is about 1/16" less in OD than the Dana Super 44 in the Vipers. The Ford pinion has a nice conical step up to the larger diameter from the pinion spline whereas the 2.72 has a right angle step up which now explains why it breaks like glass when any kind of sticky tire gets traction on it as compared to the Super 44's 3.07 with which I have never heard of anybody having a problem.
The Ford's teeth on both the ring and pinion seem to be thicker and have more contact patch ie more drag as well as a more severe helical pitch which makes it seem to sit lower relative the ring gear than the Dana sets which I am sure also contributes to more drag/ drive line loss.
Now a question about the more obvious aspect of the Ford 2.47 which is the bearing support on the back side.... This setup with bearing support on both ends seems like it would allow the ring and pinion to maintain a tighter tolerance in relation to each other within the case which should track more consistently and be able to hold more power.
Any engineers or people who know more about this subject care to elaborate on anything else?