Broken End Links
 

I was under my 4Runner last night, and discovered that both of my front sway bar end links have snapped. The last time I was working in that area was last December when I replaced my shocks, and they were fine then. I don't do any offroading, so I'm not sure what happened to snap both of them. I'm at stock height, but I do have poly bushings on my sway bar, and had them on the end links as well. Is there anything I should be looking for that might have caused this to happen and should be addressed, or should I just chalk this up to cheap parts store end links?

I discovered one of my original 1997 front sway endlinks broken 2 years ago. Might have been broken for a year or more. I removed it and never looked back.

With the front sway bar links disconnected (or the broken ones still on) how hard is it to rotate the sway bar? If the sway bar is too hard to rotate that could be what broke both your end links. If it is really stiff I would suspect the sway bar bushings are too small for the bar.

It doesn't flop around, but it moves without a huge amount of force.

I'm thinking the poly bushings are the cause for alot of these broken links I've read about. If the link is absorbing more of the pressure/tension instead of the softer bushings it makes sense to a degree.

On my mazdaspeed 3, I run polyurethane mounts and bushings to stiffen everything up for cornering and such.

On my 4runner I keep everything softer for comfort and shock absorption.

I went with poly strut mounts and the NVH definitely increased, which I didn't suspect it would have. Learned my lesson on that one.

Just my 2 cents.

The poly bushings killed the end links as the material is way stiffer than the rubber alternative. I would replace it with a MOOG end link as they are much heavier duty for the poly stuff. The bottom end link bolt can be a pain to remove as it does spin - the trick to removing it is by clamping nose pliers behind there while trying to break the nut loose. Torching the nut also helps a bit too.

I'm gonna go against the grain and say it WASN'T the super tiny difference in stiffness in the bushings and you just got shitty links. That might hold water IF you were doing something other than highway driving, and even then I'd say that's a little pushing it. Much higher chances you just received a faulty product or have something else going on, maybe incorrect length or something. Since end links are such a cheap and disposable item they typically have varying levels of quality. I was running Moog K90681 on all 4 corners and it took me 8 links just to finally have a full set that worked - either they were frozen up right out the box or started to stiffen/seize after a month. Even then I had some stamped with Moog's logo, some that weren't, some missing threads for the zerk fitting, some were tapped...
Shit happens sometimes. I broke one of MStudt's "unbreakable end links" in less than 10 minutes by driving on a very, VERY mild FSR. Despite others claiming they took them through things like the Rubicon and whatnot.