Weird Hum Coming From The Front End

Joined
Aug 3, 2014
Messages
416
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Monument
Okay so here's a long term update. I still don't know what's making the hum noise! It's still there! I did the wheel bearings and then 2 days later I bought a FJ60 and the 80 went to storage. After driving the 60 for a couple of months I started to miss the comfort of the 80 and the Cruisers swapped places. Now this vibration is not super loud and doesn't make noise unless it's over 60mph. But after running down the highway for the first time I remembered it's still making noise. Being on the gas or off the gas doesn't matter.

So since I did the wheel bearings I double checked the u-joints that have no play in them, and changed the front diff fluid with some synthetic 75w90. The old stuff was dirty but it was completely full. It's still making noise. What else can I check? The noise is not very loud (my dad can't hear it) but I can swear it doesn't sound normal and I think I can feel a slight vibration under my feet. Anything else I can check? I might pull the driveshaft this weekend even though I have no idea why it would be that considering it doesn't have castor correction and the u-joints have no play. Any other ideas?

Thanks!
 
Joined
Aug 3, 2014
Messages
416
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Monument
Any ideas? Also it's been a weirdly warm winter here but today it was pretty chilly and for the first 30-45 seconds of the drive there was a low pitched but loud whining noise. I know for a fact it's not power steering and it sounds like it's from the front end. Could this be related? I'll record a video of it tomorrow morning if it's cold enough. Weird thing is after 45 seconds it's gone.
 
Joined
Aug 3, 2014
Messages
416
Location
Monument
Still making the weird noise. Sounds like it's still maybe coming from the front passenger side but still unsure. I changed the rear diff and transfer case fluid last weekend. It finally got cold enough to do the high pitched wine when it's cold and was able to get a video. Still hard to hear through the video however. I trimmed the video where I think the noise is most prominate.

 

Proven

RTFM, STEP 6, POST
 
Joined
Apr 11, 2006
Messages
792
Location
Atlanta
Just to summarize:

The issue is most noticeable above 60 mph.
Your father doesn't notice it
The issue persists even after re-greasing wheel bearings and changing fluids in the differenetials
The sound does not increase or decrease with throttle

Things that come to my mind:

  • Fuel pump is right behind you under the 2nd row passenger seats

  • Catalytic converter whine or a loose connection on your exhaust

  • Idler pulley

  • EGR valve noise

Based off what you've posted and my brain - it is something that builds in pressure/resonance as you increase in speed but isn't affected by acceleration.

Usually drive train noises would usually change on and off throttle because the throttle applies pressure to the system. That pressure changes the sounds usually.

anyhow...just spitballing.
 
Joined
Aug 3, 2014
Messages
416
Location
Monument
Just to summarize:

The issue is most noticeable above 60 mph.
Your father doesn't notice it
The issue persists even after re-greasing wheel bearings and changing fluids in the differenetials
The sound does not increase or decrease with throttle

Things that come to my mind:

  • Fuel pump is right behind you under the 2nd row passenger seats

  • Catalytic converter whine or a loose connection on your exhaust

  • Idler pulley

  • EGR valve noise

Based off what you've posted and my brain - it is something that builds in pressure/resonance as you increase in speed but isn't affected by acceleration.

Usually drive train noises would usually change on and off throttle because the throttle applies pressure to the system. That pressure changes the sounds usually.

anyhow...just spitballing.

That really does sum it up. Those are some great points thank you so much. I know the catalytic converters are a little loose so that could be my problem. I will look at that today. Thank you so much!
 
Joined
Nov 4, 2018
Messages
12
Location
Texas
That really does sum it up. Those are some great points thank you so much. I know the catalytic converters are a little loose so that could be my problem. I will look at that today. Thank you so much!
Was there ever a definite resolution to this? I’m having the exact same issue and my mechanic can’t seem to figure it out, but he seems to think it could be a hardened transmission mount or something. Front wheel bearings have been changed, all u-joints in the drive line have been changed (they were going bad), diff fluid is new, topped off, not leaking etc.
 
Joined
Dec 3, 2015
Messages
836
Location
morro bay calif
Pull the front driveshaft lock the Center diff take it for a drive if the noise goes away you know it's the front drive shaft if the noise is still there you know it's not drive shaft related mine was making a weird hum noise after the 3-inch lift and that was the problem
 
Joined
Nov 4, 2018
Messages
12
Location
Texas
Pull the front driveshaft lock the Center diff take it for a drive if the noise goes away you know it's the front drive shaft if the noise is still there you know it's not drive shaft related mine was making a weird hum noise after the 3-inch lift and that was the problem
Front knuckles are full of grease. I just did a full front axle job at Christmas, and there is no grease migration into the front diff. I pulled the driveshaft last night and went for a drive, and the noise was still present, possibly even a little more severe.

If you had an issue with the pinion bearings wouldn’t the noise be wayyyy less severe with the driveshaft removed?

Looking back, seems like when I re-packed the Wheel bearings, The spindles were a little worn and I had trouble getting the correct pre-load. I set it with the first axle nut just fine per the FSM procedure (torque to 45 ft lbs and loosen a few times while turning, then set at 48 in lbs), but then when I installed the lock washer and torqued the second nut to 47 ft lbs the preload increased to 14-16 lbs, rather than the 6-8 lbs with just the first nut. So maybe that is my issue.... I probably should just install new spindles and bearings on both sides and see where that gets me.

Next question.... are the new spindles with bearings instead of a brass bushing worth the price premium ?

Thanks
 
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