Painful low frequency drone/pressure in cabin (2 Viewers)

[MongooseGA]

Is it solely road speed dependant or does your throttle input impact it all like with u-joints?

 

[LJE]

Is it solely road speed dependant or does your throttle input impact it all like with u-joints?

I *think* it's all roads speed dependant. Going to spend some time on the road in the next day or two trying to rebaseline & recharacterize it after all the 'fixes' I've done.

 

[RapidRob]

Oh, interesting - I'll take a look at those and likely order the two to knock it off the list.

Wouldn't that be a hoot, I didn't even know there was a bushing there. I'll have to look at that myself to understand what it does.

 

[curryitr]

I’m no expert on these things but is it possible that all the extra sound deadening you added is trapping the resonance in a certain part of the truck, or making it have a different frequency that is painful to humans?

 

[Zuberg]

Had to edit my earlier post as I had the bushing location wrong on the torsion bar crossmember. It looks like the 'support assy, front suspension' sits inside a frame crossmember. Appears the torsion bars and support assembly have to be removed to replace the bushings.

First pic below shows the support assembly with bushings circled.

Torsion bar adjustment below with bolt/bushing circled.

 

[LJE]

Alright, update here.

Some observations (and no answers):

1. It's definitely worse the higher outside temperature gets. That doesn't make sense to me, but neither does anything about this. Drove to work at ~0500 when it's 50 degrees outside - not terrible. Still there, but tolerable. Drove home at 1600 that day when it's 80 degrees outside and ow, my ears. So. Much Worse. This correlates well overall with my experience - terrible in the summer, better in the winter.
2. It's better with more crap in the back. Loaded down for Cruisers on the Rockies, it was mostly tolerable. Some days on the road were worse than others, which is confusing.
3. I ratchet-strapped the rear wing window mechanism to the floor D-rings to eliminate them vibrating the windows as a possibility. This actually changed things - rather than a 'pulsing' pain/pressure on your eardrums, it's now a constant pressure feeling - as if you were ascending/descending in an airplane but couldn't clear your ears. This would point to there being a pressure differential being created that was 'flapping' the rear wing windows, but with them ratchet strapped they can't do that any more; rather than a pulse you just get a constant pressure feeling on your ear drums. Still no audible noise.

What does that mean? No idea. I've replaced the D-pillar vents, so the cabin should vent freely. It also doesn't get better when you open a window or two - that's super confusing, because that would prevent any form of pressure differential. It does seem to go away if you open the sunroof all the way, but again, no idea what that means.


It's a good thing for this vehicle that I only found this after I put so much effort into resurrecting it. If I had less than $15K in it (I've got more than double that at this point with the lockers/leather/bumper/etc) I would roll it off a cliff.

 

[MongooseGA]

Wild shot here- What if instead of it being related to the ambient temp, it's actually something to do with whether you're running the heat or AC. Tried running with the HVAC off in the cooler/warmer duplicable conditions and seeing if the difference still exists?

 

[Zuberg]

Sorry to hear this is still an issue for you. Interesting about the rear wing windows though.

Just curious - Did you ever try replacing the torsion bar anchor bushings? If so, Any changes?