We set out to not just make a brace, but actually make sure it did something! To do that, we made a massive test fixture complete with subframe, sport differential, axles, hubs, and a driveshaft. We then welded a 12 foot long steel tube to the driveshaft and applied force with a load cell until we broke the weakest link. With our fixture we are able to apply almost 5,000 ft-lbs of force to the rear end. Here were the results:
- Test 1 - Everything stock - RH OEM axle shaft broke at 1602 ft-lbs
- Test 2 - Added JXB upgraded RH axle - LH OEM axle shaft broke at 1912 ft-lbs
- Test 3 - Added JXB upgraded LH axle - differential rear mounting bolts broke out of casing at 1939 ft-lbs
- Test 4 - Added our differential brace - RH JXB axle shaft broke at 2296 ft-lbs
- Test 5 - Repeat of 4 with new RH JXB axle - Pinion flange shaft broke at 2210 ft-lbs (possibly due to damage from snapback from previous tests when components broke suddenly)
So, what does this mean? At a MINIMUM, our diff brace added 18% strength to the Sport Differential casing. We know for sure we made it stronger than the OEM axles and even stronger than our upgraded RH axle, which nobody has broken yet in real life. That means the differential casing is no longer the weak link!
In addition, our RH axle added 43% strength compared to OEM. Our LH axle added at a MINIMUM 20% strength compared to OEM. We will continue to do more tests to see if we can find the limits of the LH axle and the casing with our brace installed.
There are some interesting things to note here. Out on the road, we do see spider gear failures at least as often as casing failures. We didn't see any spider gear failures in our testing. We also were not able to shear the driveshaft bolts, which seems to happen often in real life. I suspect the reason for this is that these failures are either related to the shock of a launch/hard shift, or they are due to fatigue over time. Our test is quasi-static, meaning we applied the force in a slow and controlled manner. This does not provide a shock to the system that may be needed to break the spider gears inside the diff. Shock also has a large effect on shearing bolts, though improper torque and reusing bolts can also affect their strength. Our gut feel is that the driveshaft bolt failures are more likely attributed to improper installation and/or too many uses.
Regardless, we were able to recreate the casing failure the differential brace aims to address and can say definitively we were able to prevent it!
