Here's where the bigger-beef argument really tachs up. The 14-bolt axleshafts (left) are 1 9/16 inches in diameter and have 30 splines. The majority of 60 shafts are 1 5/16 inches in diameter with 30 splines. That's the same size shafts that are found in rear Dana 44s. Heavy-duty 60s have 35-spline, 1 1/2-inch shafts (same as Dana 70s), but on the used market they're as scarce as truth in Washington. And contrary to some opinions, the Dana 61 is not a heavy-duty 60. According to Dana's reference book, full-float 61s ran only in mid-'70s Ford 3/4-ton 4x2 pickups and vans. They all had 1 5/16-inch axles, not 1 1/2-inch. The major difference was their higher gear ratios (3.07, 3.31) compared to stock 60s.