Hey Yotatech, its been a few years since I've been on here but I still have my trusty '95 Pickup.

I have an strange grumbling sound and vibration that pops up every once in a while. The sound seems to follow the wheel speed and I've had it happen with city and highway driving. It seems to happen more often in the colder weather. It is coming from the front end of the truck. I initially thought it may be a wheel bearing but I'm kind of at a loss as to where it is actually coming from. I've had it into a garage but they weren't able to replicate it.

I've attached an audio clip from my short drive today. I had the recorder on the steering wheel, so the turn signal relay is very audible.

Does anyone recognize this grumbling sound? The sound is right at the beginning of the clip until you hear me drive over a train crossing (around the 13 second mark) and the sound stops. The second occurrence in the clip starts at 1:45.

 

4wd engaged? Hubs locked?

 

4WD is not engaged and this one has auto (ADD) hubs.

 

Wheel speed or engine speed? If it is a manual transmission what effect does pushing in the clutch have when it is occurring..

I didn't really hear it follow the the throttle untill I heard it a few times. Sounded more like an idler bearing. A wheel bearing noise to me is more of a high pitched constant tone.

You could try a "feel" test by jacking up the front end and maybe noteing a bit of drag in certain positions. That's more likely a break issue.

Put the stethoscope to the back and see what you hear.

 

It could well be the brass bushings? When worn, you can get that weird buzz / resonant frequency build-up?
https://www.yotatech.com/forums/f116...rouble-248517/

Add means the shaft / shafts are moving, right?

I think we got it!

 

That bronze bushing failure sound is the same type of sound as the audio clip. Good find!

 

As far as I know that is correct, the shafts are always moving whether in in 2WD or 4WD. I did another test while on the road today. I engaged 4WD while moving and the sound didn't go away but it did change temporary. It could be a fluke but so far all the evidence is pointing to those bushings. They look like a PITA to replace; but they do seem like that could be the source of my issue!

Once I get to tearing this thing apart, is there any way to tell if they are indeed worn? Would there be play like this?

 

Yea. Looks like mine.
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But I can unlock. Usually.

(I've heard it once or twice, while using front driveshaft only to get to work. That lead me to search.)

No need to remove the locking hub. Just grab a half shaft near the hub. Shouldn't have any up down type play. If it moves, order new wheel bearings while you are at it, and prepare for an evening of beer and staring at parts, only to want to kill it a while later.
It's really one of those "just keep going, it will happen!" jobs.

hfgl