I have zero complaints with the factory X3 axles. My rear ones are still going strong currently at 8500 miles. My fronts have probably about 6000 on them after I switched to Smartlok. I did break one shaft in sand hollow last time I was there but it was a summers brother shaft with stock CVs. I put the stock shaft back in and have it as a spare now. The axles had summers bro shafts in when I got them.