The cam synchronizer is a common failure item in Vulcans, with a working life typically between 80-100k miles. It usually doesn't seem to do any damage if caught in time, but as the gear at the bottom of the synchronizer drives the oil pump it could (worst case scenario) theoretically destroy an engine.
There are two causes for the failure.
The first seems to be exclusive to the hall effect version of the sensor, (up to 1997), where a piece of the magnetic tab that sits on the underside of the top of the sensor breaks off and damages the vane (metal tab that sticks up out of the rotating assembly that the sensor reads) that is used to time the engine; this will throw a CEL
as the sensor is no longer functioning. The second applies to all vulcans and is what actually causes the chirping, it seems that the rotating assembly in the synchro does not recieve proper lubrication and the bearings start to fail. In either case the synchro itself will have to be replaced, and it's usually a good idea to replace the (cheap) sensor while you're at it.
The problem manifests itself a chirping coming from the transmission (driver) side of the engine
. It can be very hard to pinpoint, when mine started to fail the sound appeared to come from different places as I moved around the engine bay. When my mechanic took a stethoscopey thingy to my engine bay, he concluded that it was ghosts and I should "come back if it gets worse". From reading posts on here, and my own experience, the chirping responds to RPMs, most pronounced at idle and eventually drone out to a whine at driving speed. It also seems to be affected by heat and humidity. Mine stopped making noise (when it got cooler outside) the better part of a year before I replaced it, but I suspect that if I hadn't it would have started again when it got hot.
There's a cheap way to replace the assembly, and an expensive way.
From what I've read on here, dealers/mechanics will charge $150-$170 for the assembly, as well as 3-4 hours of labor for the replacement. I found the part (Dorman#689-107 for my 02') on RockAuto for $40 and it took me an hour to install it. RockAuto's catalog will guide you to the correct part. For mine, it was listed under camshaft synchronizer, but I have read about it possibly being listed as a distributor for earlier years. The actual replacement of the part is as simple as undoing 1 clamping bolt, removing the old assembly and installing the new one. The most time consuming part for me was cutting the plastic tray that guided the wire bundle that ran directly overtop of the assembly so that I could even get to the synchro. Whether you are comfortable with doing this yourself will depend on how stubborn you are, and whether you think you're up to digging your way to the sensor/synchro. That's the hard part.
There is some risk to doing it yourself, but only if you do it incorrectly.
The cam synchronizer is integral to engine timing, and if the new assembly is not installed with the exact same orientation as the original some serious damage could occur. Luckily, it's not that easy to mess up if you pay attention. The teeth on the bottom of the synchronizer are big enough that the vane rotates approx 10 degrees for each tooth. After removing the sensor from the top of the assembly and before touching the clamping nut that secures the synchro; if you mark the relative position of the synchronizer body on the block, and mark the position of the vane on the synchro body you can install the new synchro in the exact same position. If you make accurate marks and pay attention, it will be obvious if you are off. I replaced mine with this method and have driven approx 150 miles since without a CEL
to be seen, nor a squeak to be heard.
Good luck, I saved myself several hundred dollars doing this myself with information gleaned from the TCCA. Even if you choose to have a mechanic or dealer do the replacement, diagnosis and correction of this issue could save you some money and trouble in the long run.