I would hate to see many years of research and discussion on the forum distorted by misinformation so unless I’m really misinformed myself, the Eaton HO72 uses exactly the same carrier as the Eaton HO52; it is the 1-ton version of the axle housing however. The differences being in the backing plates brakes and drums. There was never a 4.10 available in the Eaton HO72 and in this version of the Eaton rear axle you are most likely to find a 5.17 gear ratio and occasionally the option of a 4.57 gear ratio. There have been many discussions on this subject over the years and by reviewing the archives you should be able to verify this.
The 4.10 gear was used in some 68-72 3/4- ton trucks with automatic transmission. Mine came out of a 1970 3/4-ton V8 automatic pickup.
Very nice looking truck Joe, but if your 51 has a Dana rear axle in it then it has been changed from what was originally installed at the factory. Your single picture does not indicate what engine, transmission, rear axle was installed in the truck but I would assume that if it has a Dana rear axle that the engine and transmission have also been upgraded.
Denny Graham
Sandwich, IL
