We’ve had a number of damaged rear axle threads lately. Above and below you can see the latest disaster. In this case, someone damaged the threads and then welded the axle nut in place to hold on the hub. We cut the welds to remove the nut and replace the leaking hub seal, but the axle is too far gone to re-use so we had to replace the entire assembly.
This is a reminder to be extra careful with these threads, because when they are are damaged as shown here, you need and ENTIRE new axle assembly (as shown three photos below). This is not an easy part to find.
They fail for many reasons. First, the giant nut that lives on these threads requires a special tool. A giant conventional socket will not work. You need this six-sided key, which you operate with your own ratchet handle and extension. Many people seem to use chisels to tighten these nuts, thus destroying them. Get the right tool by clicking here.
Second, the left side nut (drivers side with LHD car) has reverse threads. If you don’t know this, you might tighten and possibly strip the threads instead of loosening this nut.
And lastly, some people over-tighten these. I would use 80 ft lbs as a guide. Make sure to use the factory lock tab.
If and when you have to loosen your rear axle nuts, make sure you treat these threads with extra care!