I've now had 3 sets of aftermarket (FCP Groton) sway bar end links come loose at the upper mount (on the strut) shortly after installation. First set: hand-installed snug. Second set: air wrench snug. Third set: impact wrench and torqued snug by area indie mechanic who does very good work. They were made aware of the previous problems, and went to great lengths to make sure the nuts were properly snugged. No better.Worked loose in a short period of driving.

Each time, the top nut works loose within 20-30 miles, causing the threaded bolt to rattle around inside the hole, of course destroying the threads. The nut keeps backing off and eventually falls off.

My theories:

1) Is the self-locking nut not holding in place, and perhaps we need to use real lock washers and nuts instead ?

2) Do you need to move the wheels back and forth, and maybe even put load on them, to eliminate any "slop" after the initial tightening ? Perhaps they're not actually "tight" on first installation and snug-down, even though they feel tight and even show tight on a torque wrench ?

Both I and my indie are stumped on this one. If anybody has past experience here, I'm all ears.