Loud humming while coasting ?

[Bludozer]

Cruiser started making a loud hum/whine sound while coasting. If I am accelerating I have no problem but as soon as I stop depressing the throttle the sound appears. Any ideas for diagnosing would be greatly appreciated. First thought was pinion bearing? Not sure though.

Had a buddy of mine who is a mechanic (not a cruiserhead by any means though) listen to it and said he thinks it might be coming from the transmission. Certainly hope he's wrong - not sure why it would be making the sound only when my foot is off the throttle if that's the problem.

Also worth noting u-joints are brand new. I just upgraded the suspension as well but it was making the sound before that.

Thanks!

 

[Rivman1243]

Check your fluid levels in you diffs and transfer case. Whats the condition of the slip yokes?

 

[Bludozer]

All fluids were drained and refilled about 3k miles ago. Slip yokes look fine for a 20 year old truck nothing especially spectacular about them though.

 

[Rivman1243]

Does it do make the sound when you're decelerating i.e. Engine breaking? Or just when you're costing?

 

[Bludozer]

Both. Anytime I take my foot off the gas pedal it starts humming.

Praying for no transmission issues haha.

 

[lp2k]

When did he grease his U joints?

 

[stkybgr]

Had the same noise, ended up being my front spindles were worn and the bearings race had spun and I couldn't tightened the wheel bearings properly. I replaced the spindles and wheel bearings, problem solved.

 

[Bludozer]

Had the same noise, ended up being my front spindles were worn and the bearings race had spun and I couldn't tightened the wheel bearings properly. I replaced the spindles and wheel bearings, problem solved.

Just to be clear, you would hear nothing while accelerating or depressing the throttle at all in any way and then as soon as you removed your foot from the throttle you would hear the sound?

That is a really good thought though, hadn't considered that for some reason.

 

[stkybgr]

I never really noticed any noise until I would be coasting. Speeds were around 60mph, hum would go away when I would give it gas.

 

[06Yoda]

Mine is currently doing the same thing. Only while deceleration and my u joints have been replaced (oem). My front u joint angles seem to be pretty bad though, I'm guessing that's my problem but could be wrong.

 

[Squash]

Did you grease the slip yokes?
Overgreasing or should I say old grease and greasing can Hydro lock the driveshaft making it a solid pipe which now puts pressure on the components in line.
Either take off the rear ds to start or pull the rear slip zerk out. Watch for grease exiting which means pressure.
Being lazy I squirt some WD40, PB or brakekleen into zerk fitting and drive for a while allowing time for the spray to clean out old grease.
While driving you should notice yes or no to the hum.

This is the cheapest and easiest first step

 

[benjrblant]

I never really noticed any noise until I would be coasting. Speeds were around 60mph, hum would go away when I would give it gas.

This sounds like my symptoms exactly...

 

[Bludozer]

Did you grease the slip yokes?
Overgreasing or should I say old grease and greasing can Hydro lock the driveshaft making it a solid pipe which now puts pressure on the components in line.
Either take off the rear ds to start or pull the rear slip zerk out. Watch for grease exiting which means pressure.
Being lazy I squirt some WD40, PB or brakekleen into zerk fitting and drive for a while allowing time for the spray to clean out old grease.
While driving you should notice yes or no to the hum.

This is the cheapest and easiest first step

I like cheap and easy. Will be trying this, thanks!

 

[9780LC]

I had this noise happen and it was indeed the rear pinion bearing.

 

[Matt Zimmer]

How are your repairs/troubleshooting going on the hum noise? I have the same issue.

 

[bajaphile]

Generally this is the rear u-joint needing some grease.

That being said, I'm battling this vibration & noise again even after replacing the u-joints with OEM and installing adjustable upper arms to re-set the pinion angle. I lube my u-joint and it goes away for about 50 miles...then comes back!

I've had my 4.88's for about 10k, set up by Zuk. There appears to be a tiny bit of diff fluid dripping from the front of the rear pinion seal. I can't image the pinion bearing failing. Just annoying to have addressed "everything" back there to get rid of it and its still present and very noticeable on the highway.

 

[ccslider]

I'm having this same issue. I haven't looked into it yet, I figured it was the u-joints which I'm planning on replacing soon.

Goes away when on gas, hums when off.

Interested in what everyone else finds.

 

[RyRoRyan]

I have the exact same issue. Its been this way since I bought it a year ago. For me it sounds like its coming from the front diff so I am assuming pinon. When I got it, the PO's PO put Nitro 5.29's in it, and I just thought this was a result of said install. Looks like a repair is in order.

I saw another thread that was talking about popping while articulating. I as well have this too up front. No clicks while turning so I know its not birfs. I have the Nitro chromoly birfs and they have been amazing. Something tells me that it might be a rocker arm bolt not tight enough because the bushing visually look in great condition. I just need to get a prybar and some wrenches under there and test/check it all out.

 

[ccslider]

I have the exact same issue. Its been this way since I bought it a year ago. For me it sounds like its coming from the front diff so I am assuming pinon. When I got it, the PO's PO put Nitro 5.29's in it, and I just thought this was a result of said install. Looks like a repair is in order.

I saw another thread that was talking about popping while articulating. I as well have this too up front. No clicks while turning so I know its not birfs. I have the Nitro chromoly birfs and they have been amazing. Something tells me that it might be a rocker arm bolt not tight enough because the bushing visually look in great condition. I just need to get a prybar and some wrenches under there and test/check it all out.

Rocker arm bolt? Rockers are valve train. Do you mean radius arm?

 

[RyRoRyan]

Rocker arm bolt? Rockers are valve train. Do you mean radius arm?

Sorry, yes radius arm. Havent had coffee yet.