I've replaced a handful of broken double acting rods, and fixed maybe a couple dozen that buzzed. Most of the time they work great. I have to say I'm surprised how well they work. Before I worked on guitars, I worked for a small company that manufactured racing bicycles. We made TIG welded steel frames. The welding that I've seen on truss rods (domestic and imported) would have ended up in the dumpster at the bike company. And yet, they seem to work fine, and go on working fine. I suppose it stands to reason that a truss rod doesn't have to endure the fatigue cycles that a bicycle does. (And you don't land on your face on the pavement if it fails.) The most common flaws are small cracks in the weld itself. If you look at the weld through a decent loupe, or hand magnifier, these are easy to spot. Most of the rods I've seen had these cracks. In my experience, these cracks don't propagate in service unless they are quite large. On a bicycle, even a small crack would quickly cause a failure. So what caused the failures on the rods I replaced? Most of these had the threads fouled by the weld puddle. If you look closely, you can usually see if this is a problem before you install the rod. You can also put one end of the rod in a vice and turn it both ways for 1 1/2 turns to make sure it functions smoothly. Slide a piece of plastic conduit over the rod before you test it. The rod needs to be supported or it may buckle near the nut. Something else to inspect: sometimes the broach for the allen socket is poorly made. Make sure that the allen wrench can engage at least 3/16 inch, and that the socket is hexagonal, not just a circle with some dents in its perimeter. A smoothly working rod won't do you any good if the wrench ends up just spinning in its socket. Also: make sure that the silicone you use to bed the rod is non-corrosive. Dow Corning 748 available from McMaster is excellent. What to do about a rod that buzzes after the guitar is built? It's not that difficult to fill the truss rod cavity with silicone after the fact. I pull the second fret, drill a 1/16 hole into the truss rod cavity at an angle, and inject a low viscosity, non-corrosive silicone through a hypodermic needle until it flows out inside the guitar. The first time you try this, you'll be swearing at me, but after the first few, it's pretty routine. It's definitely an improvement on pulling the finger board.
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![[xx(]](./images/smilies/smiley11.gif "Dead")
He was very patient while I came to the OLF and sought advice...Mario came to the rescue and told me how to fix the rod, and opined on the rod that I was using at the time... 
...I tossed the remaining ones I'd bought in the trash, went to the Allied rod and NEVER plan to change...I love this rod and as far as expense goes...remember, the truss rod is one of the less expensive parts of an otherwise very expensive project...and one of the worst things to overcome if it fails...my advice, for what it's worth, is DON'T skimp here!