The Dana 70 is a super-tough (and heavy) axle that is a favorite for towing and hard-core 'wheeling. One of the benefits to a '70 is that there are a number of different pinion yoke sizes available, including a 1410-series yoke. Be careful though, because different housing castings used different sizes of pinion bearings due to different sizes of pinion bores.
Applications: Front and rear.
Type: Most full-floating with some rare semi-floating in commercial applications.
Spline count: 23, 32 or 35.
Factory ratios: 3.54:1 through 7.17:1.
Maximum tire size for stock axle: 44-inch.
Strong point: Large teeth on ring-and-pinion.
Weak point: Small diameter pinion shaft (same as found on Dana 60).
Junkyard jewel: Rarely seen but known to exist are open-knuckle front axles with disc brakes. A rear heavy-duty '70 was fitted under '73-'91 Chevy dualie pickups, and it has larger-than-normal carrier bearings.
Building secrets: When rebuilding, make sure that any stock oil-restricting device is left in the pinion area. This keeps lube in the pinion-bearing area at a higher level and retains it longer. Custom Differentials says that a number of '70s come to them with the oil-restricting devices removed.
Aftermarket alternatives: Dynatrac, Custom Differentials.