It's a risk you take when running locked 35s on stock front shafts. I do wheel very hard trails. This was on trail #27, one of the hardest trails, at Redbird SRA in Indiana.

 

Do some reading on losing the C Clips on the stock ujoints. That pic may have been a ujoint failure due to losing the clip, (which let the cap fall off, which ended up exploding the ears as well) and nothing to do with being locked or open.

This one may help explain it.
http://project-jk.com/jeep-jk-tech/f...l-circle-clips

 

Thank you that also helped. And he said he wheeled very hard trails i couldnt imagin doing anything to extreme.

 

The longer you drive with stock axles the more likely a C-clip issue is, because I wheel a lot it happened within 6 months of putting 35s on. All though a lot of people equate rock crawling with extreme, mud probably breaks more axles. A spinning tire that suddenly gets full traction puts and incredible amount of stress on the axle, if that axle is locked it's even worse. If you put lockers in, use the front sparingly, only when absolutely needed. I only use my fronts 10% of the time I have the rear engaged. Getting stuck and recovered is not a bad thing. I should have stuck with the three try's and then strap or winch rule. But I almost had it so went for it a 4th time with a little more skinny peddle.