Loud howling/humming sound coming from front end

[Vada]

Hi all, so I have this 2006 KJ 3.7l, since I got the thing it's had a bad humming/howling type sound accamponied by a little vibration felt both under the passenger and the driver side as well as in the steering wheel. This happens at roughly 35kms and up, at highway speeds the sound is less noticable but still there a little bit. The sound is apparent with speed, so when I apply the brake you can hear it and feel it slowing down with the drive components. I also popped the car into neutral and I can still hear it. At first I assumed wheel bearings, so i replaced both front wheel bearings and to my dissapoinment the noise was still there. I've also looked for any scraping parts, I've replaced both front brakes still no luck.
I'm now wondering if the sound is coming from a bad pinion bearing on either the front diff or the transfer case end.
So, my question is- has anyone else ever had this?
If so, what would be an easy way to go around properly diagnosing and solving this?

I thank you muchly.

[Fishframe]

This could be a number of things. I recommend you type this in to a google search : jeep kj humming sound vibration forum , and have a read through some of those forum threads to see which ones appear most like the problem you are having. You should be able to narrow it down from there.

[indiedog]

I had similar several years ago on mine. I thought it was the clutch throw out bearing (mine is a manual) but it turned out to be the CV joint at the front of the rear drive shaft. Take a look at that and see if it's worn. I believe there's a ford unit that will fit. Note the front driveshaft also uses a CV joint so check that too though the rear is the one that does most of the work.

If you are in Brisbane I went to a place on the northside who did a good job sorting it out for me.

[Vada]

Cheers for the replies
As for the drive shaft components, only my front drive shaft has cvs on it (the rear has 2 u joints that I've replaced aswell) and I know they're good because I actually snapped the front drive shaft a few weeks into owning it, right off from the diff end and put a new one in. I should have mentioned this in the original post but that is also why I'm concerned with it being something to do with the diff, could bad bearing in a diff cause a drive shaft to snap? I had the car in some soft sand at the time, and I know that the car did a lot of towing prior to my ownership, I never did find a good reason though as to what happened, I just put it down to abuse..
There's also cvs that go to the front wheels, but they aren't showing any obvious signs of wear.. could they make a sound such as this and not be obviously detectable? I haven't noticed any clicking sounds that people usually say accompanies a bad cv but still you never know..
Also, I've tried to look for information about this on the internet and they all seem to come back to being either a wheel bearing or a drive shaft which I've ruled out.
Cheers

[glend]

Easiest way to tell is to drain the diff fluid, if you have metal shards in there it probably needs a rebuild. Not sure about your diff, as I had the CRD, but stock Chrysler diffs don't usually have a bottom drain hole, so you might have to lossen off the plate and left it drain out the bottom. The rear diff does have a breather hole on top, if you (or previous owner) have submerged the diff to the top of the breather hose, it may have water in it (this is bad).
A history of towing, may indicate a poor diff service history. I think taking it to a diff specialist might be the easiest way to sort it out. The Chrysler Corp rear end has parts and rebuild kits available.
As always, with KJs of this age, unless you know the original owner or have a very good service history, don't trust the seller.

[Jeep'ers]

I found it to be my front drive shaft when my 05 kj did it... if you’ve lifted your kj a little, like I did mine the boots on the cv joints front and rear wear out and grease dries out or worse crap gets in there and bearing go... replaced the shaft and the vibration and noise went...

Funny my jku has just done the same thing...


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[BeagleCamper]

Consider the transfer case. I have. CRD with 220K approx & noise from Thad area gradually increased last 40K.