Mystery bass rattle - truss or stiffening rod?

markuus99

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Having issues with a mystery buzz/rattle on my parts P-bass I built in 2021. (Warmoth neck, MIM Fender body).

Some months ago, I started noticing a buzz/rattle just hitting a low F note on the first fret of the low E. I adjusted the truss rod and tried a few different amounts of relief but no dice. Still rattled- even with high action.

Next, I brought down the nut slot a bit, thinking perhaps it was too high and I wasn’t fretting the note cleanly enough as a result. Dialed that in and no still no change.

I then start noticing a buzz on the low B flat note fretted on the 6th fret of the low E in addition to the low F. So now I think it’s definitely a sympathetic vibration and some hardware is rattling. I checked all my screws on the tuners, string tree, etc. I even swapped around tuners to try to isolate it. No change.

I also had an issue with the tuner bushings starting to pull up out of their holes. I had opened up the holes slightly with sandpaper when I installed them and did slightly too much. I took the bushings out, put some Titebond on them, and then reinserted so the glue would fill the extra space in there. They seemed to stay put, but the bushings weren’t perfectly seated because I just pushed them in by hand.

To see if this was the issue, I put together a little DIY bushing tool with a machine bolt, two washers, a wing nut, and some felt for padding. This worked well in pushing the bushings that last little tiny bit and are now very securely seated in their holes.

The rattle is now much worse- extremely loud and metallic ugly buzz coming from somewhere on or near headstock. It’s really hard to pinpoint its exact location. It’s as if fully seating the bushings made the vibration transfer better and the rattle got worse.

I’m worried the truss rod or (maybe more likely) one of the steel stiffening bars is the culprit. It’s definitely not fret buzz and I’ve done everything I can think of to address hardware rattling on the headstock.

Has anyone encountered this?
Is there a good way to confirm my suspicion?
Anything else I could rule out?
 
Since it's a mim body do you have the mim neck to swap and hear if it occurs again. That would do it. Also did you swap the tuners. Remove one at a time and see if it's the tuner. Did you bring it to a Luther? It seems to me so unlikely to be the truss rod. But who knows. I'm betting it's a tuner issue.
 
It certainly sounds like sympathetic vibration. Try removing one tuner and bushing at a time to see if you can isolate it. Try the low E first. It is less likely to be the truss rod.
 
I dont have an MIM neck- this was a parts build using a Fender replacement body.

So I think last thing that I haven’t ruled out on the headstock is the bushing itself, probably on the low E. The buzzing is worse playing Bb on the E string vs the Bb on the A string.

The buzzing getting worse does seem to correspond to my attempts to address the loose fit of the bushings, though it’s a bit counterintuitive to me that the rattle would get worse as I’ve made the bushing fit more snug in its hole.

I have tried dampening the tuner and bushing with my hand in several places but that doesn’t seem to have any effect at all.

I’ll try removing the E string bushing and see if I can get any rattle from the Bb on the A string.
 
Well I’ve done some more listening and alternately removed tuners and I do think it’s tuner related. So that’s good.

Only problem is the bushings are now so secure I can’t get them out. I’l have to get or make a little tool to help me.

I’m unsure how to address if the bushing is the problem. I wonder if the glue didn’t completely fill the void in there and that’s the issue. I could try thin super glue to seep into all gaps around the bushing I suppose, or try using plumbers tape around the bushing.

But first I gotta get this bushing out so I can narrow down the culprit….
 
I don't see how the problem could be the bushings themselves if they're so tight you can't push them out easily.
 
What variety of tuners and bushings do you have?

Do you have any photos?

I don't see how the problem could be the bushings themselves if they're so tight you can't push them out easily.

It could be the interaction of the tuner with the bushing, possibly worsened when the bushing was tightened.
 
@triple jim I don't either. That's what made me start to suspect the truss rod or stiffening rods, but listening close it really appears to be related to the tuners.

@stratamania The interaction of tuner and bushing seems to track with what I'm hearing, but I'm unsure of how to address that if so. If it is that, it's happening on more than one tuner as I have alternately removed each tuner and I've never eliminated the buzz.

These are Schaller BM bass tuners purchased from Warmoth. I am using the bushings that came with the tuners, so not mixing and matching or anything.

To recap:
  • I think buzz/rattle first occurred when I used some Titebond to improve fit of bushings
  • The rattle got worse when I used a tool to better seat the bushings
  • I tightened and then removed the string tree, but no change
  • I removed the G and D tuners together- still rattles
  • I removed the E string tuner - still rattles
  • I removed A string tuner - still rattles
  • Physical holding the tuners does not eliminate the rattle
I tried with only a single tuner on at a time, but without the heavy bass string tension, the neck goes into a backbow and I can't fret cleanly anyway.

Plucking softly sort of eliminates it, but it doesn't have to be a plucked very hard to get the buzz.
 
@triple jim Knocking on the neck, I get a slight metallic ringing I can only hear if I'm close to headstock area. Seems to come from front of headstock.

Here's a video of the rattle on the low Bb on the E string

One theory I have is when I used the glue, some excess came to the surface of the headstock under the bushing, leading to the bushing not sitting perfectly flat, meaning it's at a very slight angle in relation to the shaft of the tuner. So that created an opportunity for the tuner to vibrate against the bushing in a way it wouldn't otherwise.

I guess the solution there would be removing the bushing, cleaning up any excess glue at the surface, then replacing the bushing.

Another thing I might try is simply switching to HipShot Ultralites in the 1/2" size. These don't use traditional bushings, but have the more modern threaded style, so that could possibly eliminate the issue. I do have some neck dive issues, so was considering doing that anyway.
 
@Rick I think I'll do that. I was afraid the issue was in fact not the tuners at all, and I certainly don't want to buy and install the new tuners only to have the problem recur. But at this point I feel pretty confident that's what's going on.
 
I guess the solution there would be removing the bushing, cleaning up any excess glue at the surface, then replacing the bushing.

It sounds very similar to a tuner I had on a bass where the washer under the screw type attachment was rattling. That simply needed tightening. Removing hardened excess glue may very well solve it as that might be causing a vibration. A good idea to get rid of the glue in any case which would also be the case if changing tuners.

Another thing I might try is simply switching to HipShot Ultralites in the 1/2" size. These don't use traditional bushings, but have the more modern threaded style, so that could possibly eliminate the issue. I do have some neck dive issues, so was considering doing that anyway.

The only thing with that is you have bigger tuner holes around 11/16" so the fit is way off. A better choice for the tuner holes you have would be the Schaller BM4 tuners that use a screw in threaded style and two pin system and are also about half the weight. https://warmoth.com/bm-light-4
 
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@stratamania Hipshot makes the Ultralite in two sizes, and the 1/2" post size fits a 11/16" headstock ream, so should be all good.
https://hipshotproducts.com/products/hb6-1-2-ultralite-bass-tuning-machine

The Hipshots cost a little more than those Schallers, but it looks like the light Schallers specificy a slightly different hole size and require index holes, which I'd rather not have to deal with. I was able to find the larger Hipshots elsewhere for a bit cheaper than the Hipshot site as well.

I need to get a few things I don't have to get these bushings out of the headstock. We'll see what it looks like under there once I get them off. I'll remove any excess glue regardless.


This has been a weird one. As always thanks for all the thoughts and guidance here.
 
Welp.

I made a little tool to remove the bushings. I took 1" to 1.25" PVC pipe coupler, put some felt on the bottom, ran a 5/16" bolt through it with washers and a wingnut, and used a socket to push the bushing out from below. No problem.

Just installed the new Hipshot tuners (and while they do solve the neck dive issue) the neck is still rattling! Exactly the same as before.

There was a bit of extra glue under the bushings, but it mostly flaked off the bushings as soon as I removed them. There was a bit of extra glue on the headstock, but not much. I cleaned the surface with naphtha and then scraped excess glue off with a razor blade with Scotch tape on either side.

I can't believe it. I'll try a few more things, but I'm basically back to thinking this is a truss or stiffening rod rattle.
 
@stratamania So I sort of kind of fixed it.

I got out my fret rocker and found a couple of slightly high frets (3rd and 8th frets). I spot leveled those frets and the buzz is (mostly) gone. They weren’t very high- just a few passes with sandpaper on a block did it and then a quick recrown and polish I have still been able to get the rattle a few times since I did that, but not consistently. The frets seem well seated in their slots- I can’t slide a piece of paper under them and I knocked them with a soft mallet just in case.

Two things I had figured out- one was that muting well behind the fretted note (toward the nut, including fretted string) was pretty effective at stopping the buzz. I had to stretch way back behind the fretted note to stop it though.

I also realized I could get the buzz on the same frets even if I tuned the string up or down a half step. So it maybe wasn’t specifically a sympathetic rattle based on the exact pitch.

Again it’s not 100% gone but I have a real hard time getting it now. This was definitely more than just fret buzz, but it’s like the string buzzing on the fret is causing a sympathetic rattle. And specifically seems like a sort of string buzz behind the fretted note on the same string, so that’s kind of weird.

Still rather confusing to me, but much better now…
 
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