One of the best upgrades you can make to your CJ if you're going to keep the AMC20 (I've got a set in mine...).
The Moser axle was an aftermarket replacement for the OEM rear axle shafts. When the OEM axle breaks, the axle shaft comes out of the housing... with the wheel attached. That means you can be doing 70mph on the freeway and one of your rear axles can pass you. It's not going to be a good few minutes.
Here's a good primer on the AMC20
Yes, … No, … Not exactly, … but very misleading.
ALL semi-floating rear axles can slip out of the housing. For a Model 20 anyway, the axle doesn’t hold itself in place. The axle bearings hold the axles in place. Some axles have clips at the differential, the Model 20 does not.
In a semi-floater, the rear axle is supported by an axle bearing outboard and the differential carrier inboard. The axles support the weight of the rear of the Jeep. If you were to break an axle, there would be two pieces each only supported at one end. With the weight of the Jeep on the piece of axle only supported in one place, the axle would be free to flop around inside the housing. The resulting wobble would eventually destroy the axle bearing. If run long enough, yeah, the rear wheel, tire, brake drum and piece of axle could slip out the end of the axle and drop that rear corner of the Jeep to the pavement.
The one-piece axle does little or nothing to address this problem. One might argue that the axles are a bit stronger or that the axle bearings are slightly better but still, at the end of the day, it’s a semi-floater. If this problem is a concern for you, full-floating axles are a better solution. That’s what I have, the Summers Bros, full floater conversion.
Full floaters support the weight with hubs and wheel bearings like on your front wheels, no weight is supported by the axles. My Summers Bros. use the same bearings and seal as my front hubs. I can and have removed my rear axles and driven at 70mph.
The one piece axles eliminate the splined joint between the flange and the axles. If you should break an axle, you would still have the same problems of a semi-floater.