Used in 1976-and-later Jeep CJs, the Model 20 rearend is both strong and weak. An 8 3/4-inch-diameter ring gear provides strength; weaknesses are the housing itself and the axle-to-hub retaining method. Converting to one-piece axles or full-floaters gives this axle better stamina.
The Model 30, with a 7 1/8-inch-diameter ring gear, was the standard front differential in some 1972-75 CJ-5s and all 1975-and-later CJ-5s and CJ-7s. It is still used in the front of Cherokees and Comanches, and will probably appear in the front of the Grand Cherokee
All domestic manufacturers have used Dana axles, and the 44, with its 8 1/2-inch ring gear, is likely to be a step up on anything smaller than a 1/2-ton. A narrowed 44 could be the hot ticket for vehicles smaller than a full-size sport-utility. Some Jeep CJ's and most J-10/J-20s and Grand Wagoneers used this rear axle.