The downfall of installing a big, beefy front axle has always been that it's, well, big. Weight is increased and clearance is decreased, plus there's all the swapping issues to contend with. With fullsized rigs, swapping in a Dana 60 is not a big technical issue. With smaller rigs, for the aforementioned reasons and others, it can be a huge one. That's why the alloy shafts and super-strength U-joints have become such an important equalizer because you can have an axle nearly equal in strength to the D60 but in a lighter and more compact size. This applies to Dana 44/GM 10-bolt sizes as well as Dana 30s, Toyotas and some other axles as well.
Keep in mind that beefing an axle is a holistic exercise, meaning you have to think of the whole axle rather than just a few of its parts. When you increase the strength of one part radically, you are putting another one at risk. The idea is to have all parts at about an equal level, ideally with the most easily replaced part as the weakest. This is exactly what the OE manufacturer did, as you will see below, alongside some averaged results for aftermarket products.
Note: Dana 44-sized components used for illustration purposes. Tensile strength (when it breaks) shown.
| ||Stock Strength ||Aftermarket Strength|
|297 U-Joint ||4,600 lb-ft (3) ||10,000 lb-ft (3)|
|Outer Axle (4) ||2620 lb-ft (*)(1) ||6,000 lb-ft (*)(2)|
|Inner Axle (5) ||2610 lb-ft (*)(1) ||6,595 lb-ft (*)(2)|
|Carrier, 2-pinion ||(6) ||+60 percent (7)|
|Carrier, locker ||+100 percent (8)|
|Ring-and-pinion ||(9) ||(9)|
|Locking Hub ||3,300 lb-ft (10) ||5,400 lb-ft (10)|
|(*)= Values calculated from typical materials|
1. SAE 1040 carbon steel
2. SAE 4340 alloy steel
3. Values based on similar destructive testing. The OE manufacturer's rating for a 1310 series, 297-size joint is much lower ... about 1,600 lb-ft. This lower number is the point where permanent deformation begins to occur.
4. Minimum diameter 1.10 inches at splines.
5. Minimum diameter, 1.10 inches at the necked-down section. A non-necked 30-spline axle (1.21 inches minor spline diameter) of the same material would be approximately 30 percent stronger.
6. We have to assume that the OE carrier is of similar strength to the rest of the components, but we could not find an engineer to give us a useful number.
7. The choice shown here is a high-quality, two-pinion aftermarket limited slip, because few significantly stronger-than-stock aftermarket open carriers are built. All of this is really tricky to calculate. After polling engineers and experts, we finally decided to put down an average based on the improvements found on a typical aftermarket carrier made of a higher-quality-than-OE ductile cast iron and made some stouter by design. Some OE carriers are very stout, some are not, so the benefits could vary.
8. Many lockers use a high-grade forged steel in their construction, which may put them at an even higher strata than the best cast iron. Again, this estimate based on comparing materials and design.
9. Since the OE and the aftermarket both generally use SAE 8620 alloy steel, assuming no flaws, the OE and aftermarket are essentially equal in terms of strength. There may be other issues of quality, but that's another discussion. The biggest strength factor in the medium-sized ring-and-pinions (around 8.5 inches) is the gear ratio. Ratios lower than 4.56:1 tend to reduce the strength of the gearset because there are fewer teeth on the pinion. The more teeth the pinion has in mesh with the ring gear, the stronger the gearset, and vice versa.
10. Based on industry averages. Some units may be higher or lower.
Randy's Ring & Pinion