1972 K20 Rearend ID

[Beast72]

For the past 3 years i have wondered what rearend is in my truck. Today i started tearing it apart to fix an on going bearing whine and now i need to know. All the catalogs that i have say that my 1972 3/4 ton 4x4 will have either a dana 60 or a 12 bolt. I know different because I have a 10 bolt rear and the cover is completely round and therefore is not a dana. There are no tags and the rear end has no shoulder where the axle tubes meet the center pumpkin section. I have everything apart and can get matching numbers for the bearings however one inside race is part of the pinion and and can either machine it(which i will probably do anyway) or buy a new ring and pinion. The auto parts stores keep bringing up the rear numbers HO52 and HO72.The ring measures either 10" or 10.25" across. Do i have an eaton rear end? And if so, how do i get parts, a ring and pinion for example. Oh yeah, the gearing is 4.10 and both "GM" and "1972" are stamped on the ring and pinion. Thanks for the help and maybe i'm not the only person wondering what kind of rear is in my truck.

[1969 GMC]

Hello,

your rearend is in fact an Eaton H052 axle. It is also sometimes incorrectly called a 10 bolt because of the 10 bolts holding the diff cover on. It is a pretty stout axle, the one I have waiting to go under my truck has a factory Detroit Locker in it. My ring gear measured right at 10.5".

You can still buy new gears for these. Randy's Ring and Pinion is one vendor that sells new R&P sets. I believe the only ratios you can buy new are 4.11 and 4.57.

The only difference between the H052 and the H072 is that the 72 has larger drums & backing plates, to provide greater braking capability in a one ton truck. The 52 had smaller brakes and was used in 3/4 tons, like yours.

[Beast72]

Thanks for the help. Now i can finish rebuilding my truck. I am getting tired of looking at bearings. After this project i will have replaced all but the front axle wheel bearings.