New noise, getting nervous, need advice.

[jnaut]

Over the last few days, I've noticed a very, VERY subtle 'buzzing' noise at low to moderate speeds. Generally, it seems to come from the rear end. It sounds a bit like someone in a field nearby is using a leafblower. It revs up when I speed up and slows down when I slow down. I dropped the transmission into neutral and the buzzing noise continues.

Again, very subtle... not loud at all, pretty much have to turn off the stereo and close the windows to hear it.

With my limited mechanical knowledge, I'm concerned it may be a rear-diff problem. What's the best way to do a check myself?

Or, so I don't preload the thread, is it possible it's not a diff problem, or not a problem at all?

 

[Powerslave]

I had this kind of problem with a Mini Van, but it was more of a whining-buzz noise. The pitch when up with speed (to a point > 35MPH where you could not hear it anymore), and down as I slowed. It was the rear end, it was going... Nor sure what yours is, but that's what it was on the Astro work van I had 3 years ago...

 

[jnaut]

I had this kind of problem with a Mini Van, but it was more of a whining-buzz noise. The pitch when up with speed (to a point > 35MPH where you could not hear it anymore), and down as I slowed. It was the rear end, it was going... Nor sure what yours is, but that's what it was on the Astro work van I had 3 years ago...

By 'rear end' do you mean the diff or the entire assembly?

edit: I just looked under the libby, no sign of fluid leakage or anything...

 

[sleeve]

First, check the fluid to make sure your rear diff isn't low. [probably not but it's always nice to start with the easy stuff]

Next, Jack up the rear end (chocking the front wheels) and turn each wheel by hand. If the noise shows up - it's pobably a bearing that is going bad on one side of the axle.

If you don't hear any noise - it could be the pinion bearing which won't spin while you free wheel the tire. Or it could also be the U-joints.

 

[jnaut]

First, check the fluid to make sure your rear diff isn't low. [probably not but it's always nice to start with the easy stuff]

Next, Jack up the rear end (chocking the front wheels) and turn each wheel by hand. If the noise shows up - it's pobably a bearing that is going bad on one side of the axle.

If you don't hear any noise - it could be the pinion bearing which won't spin while you free wheel the tire. Or it could also be the U-joints.

Thanks for all the responses, guys, you too Powerslave.

I'll try this tonight-- maybe tomorrow if I can't get to it. I have a couple of jack stands so I'm anxious to try the wheel spin idea. I'll definitely check fluid level tonight.

A friend did mention the possibility of U-joints.

 

[ChiefRudy]

My KJ has been giving off a hum every now and then sincethe day i bought it. It does around 35mph and when the RPMs are kinda low. Does it more so when i'm going up a hill. I've already had the diffs services at 12k and it still did afterwards.

 

[jnaut]

I haven't had a chance to jack it up yet and spin the tires, but I did get a chance to look at the diff oil level. While at work, a friend convinced me to crawl under it (in my work clothes) and peel the rubber fill cap. While I didn't pull the fill cap all the way off, the instant I started to peel it back, diff oil started dripping down the cover and my fingers. So I'm going to presume that oil level isn't a problem.

I may be removing the diff cover this weekend to do a full inspection-- look for metal filings etc. Any further advice, or what to look for appreciated.

Oh, and I was able to clock the sound a little more accurately, it's most prominent between 18 and 25mph. And I'm not sure if I'm just more aware of it now, but it seems to be getting louder-- but I'm not willing to say it really is. It may just be my perception.

 

[Greenjeep]

I had the exact same symptoms, at just a little bit higher rate of speed, about 25-30 mph. It started as a noise, then progressively turned into the whole jeep shaking. I'm not sure exactly how it went bad, but I ended up getting a new drive shaft. I don't know what you could look for in this situation, as it even took the dealership 2 days and about 12 hours to finally figure out that it was the driveshaft itself. I know this isn't much help, but at least this gives you a little more insight as to where to look?

 

[jnaut]

I had the exact same symptoms, at just a little bit higher rate of speed, about 25-30 mph. It started as a noise, then progressively turned into the whole jeep shaking. I'm not sure exactly how it went bad, but I ended up getting a new drive shaft. I don't know what you could look for in this situation, as it even took the dealership 2 days and about 12 hours to finally figure out that it was the driveshaft itself. I know this isn't much help, but at least this gives you a little more insight as to where to look?

The driveshaft?!!

Whelp, I'm kind of hoping that the driveshaft isn't the problem, but if I wanted to at least rule that out, what does one look for--- I'm assuming it was the U-Joints in the shaft, right? I mean, the 'shaft' itself is just a piece of tubular metal, so it was the connecting joints, right?

Thus far, in my situation, no noticable change in handling or any shaking is occurring. Just the noise itself.

 

[Greenjeep]

I believe it was one of the u-joints that went bad. My Jeep was still covered under warranty, so I didn't ask too many questions. In my case, it was hard for them to pinpoint where the problem source was, until they had a drivetrain specialist look at it and take some pieces off until he was able to find the faulty shaft. From what I understand there was no obvious signs just looking at the drivetrain. I would recommend taking the u-joints apart (if you know what you're doing), and looking at them and/or taking them to a mechanic to look at them, although personally I would only do that as a last resort.

 

[sleeve]

JNAUT,

to check for bad u-joints drive around on the highway for a while. Head back to your drive way and then crawl under the KJ and feel the U-joint caps. If they are really hot to the touch, than the u-joints are going to be very suspect.

U-joints are a wearable item. Some last 50,000 miles and some last 200,000 miles. I would bet that your joints are in the process of going out. Espeically if your diff fluid is full.

 

[jnaut]

JNAUT,

to check for bad u-joints drive around on the highway for a while. Head back to your drive way and then crawl under the KJ and feel the U-joint caps. If they are really hot to the touch, than the u-joints are going to be very suspect.

U-joints are a wearable item. Some last 50,000 miles and some last 200,000 miles. I would bet that your joints are in the process of going out. Espeically if your diff fluid is full.

sad2.gif

So, to be clear on this, should the u-joints be really hot if they're bad? How hot or warm should they be if they're not? Ie, will they be cold if they're good?

What's the ball-park figure to fix the shaft u-joints if they're bad?

Edit: I'm reading online that U-Joint replacement on shafts is pretty easy...once the shaft is removed. So, how hard is it to remove the driveshaft on the KJ?

 

[sleeve]

Really hot = bad joints.

The bearing caps will get warm from normal usage due to the friction. But if they are bad and grinding than the caps will start to get hot to the touch.

I would say around luke warm = OK.


You'll have to unbolt the DS from the pinion flange - and slide out? I haven't looked lately.

 

[jnaut]

Really hot = bad joints.

The bearing caps will get warm from normal usage due to the friction. But if they are bad and grinding than the caps will start to get hot to the touch.

I would say around luke warm = OK.


You'll have to unbolt the DS from the pinion flange - and slide out? I haven't looked lately.

Did some reading and talked to a friend today. He basically said that if it's bad shaft u-joints, that should be pretty easy and cheap. I concur.

However: I was able to jack Prince of Blackness up on the stands tonight, I got the tires spinning pretty fast-- as fast as I could get them spinning by hand-- and there was no detectable noise. So now I'm either going to be looking at shaft u-joints, or possibly just letting the noise do whatever it's going to do and see what happens.

ONe last theory, however. My handbrake on my KJ has acted up twice. Once I had a ratchet assembly replaced under warranty, and now some three years later, the handbrake is flakey. I park on a sloped driveway and when I pull it, it actually won't hold the car. I release it, pull it again, and then it holds the car. I know I either need a repair or adjustment. Could that be making the noise?

 

[jnaut]

Ok, was able to get the jeep diff cover off for inspection. On the bottom of the pumpkin, the oil seemed very sludgy. I've had every regular service from the dealer. However, I'm not sure how they change the oil. I suspect the pump it out. This, of course is assuming they actually changed it.

I did run a magnet along the bottom of the pumkin and found some very, very small metal filings. Nothing dramatic, but even though the magnet was very sludgy, you could see the small spikey filings standing up on top of the magnet.

Pics:

Inside diff cover:

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Inside diff...wear patterns etc:

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Sludge in bottom of pupkin:

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Also, because some were suggesting looking at shaft U joint, I did some driving on the highway, and ujoint was not hot. But both my friend and I noticed a slight amount of oil on one part:

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[jnaut]

*bump*

 

[sleeve]

J,

The sludge is normal after years of not removing the diff cover. Some of that metal might have gotten into the bearing surfaces of the pinion and that might be what is causing your problems.

At this point it might be time to start replacing some parts (starting with the u-joints) to eliminate some possibilities.

 

[kj924]

Ok, was able to get the jeep diff cover off for inspection. On the bottom of the pumpkin, the oil seemed very sludgy. I've had every regular service from the dealer. However, I'm not sure how they change the oil. I suspect the pump it out. This, of course is assuming they actually changed it.

I did run a magnet along the bottom of the pumkin and found some very, very small metal filings. Nothing dramatic, but even though the magnet was very sludgy, you could see the small spikey filings standing up on top of the magnet.

Pics:

Inside diff cover:

You must be registered for see images attach

Inside diff...wear patterns etc:

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

Sludge in bottom of pupkin:

You must be registered for see images attach

Also, because some were suggesting looking at shaft U joint, I did some driving on the highway, and ujoint was not hot. But both my friend and I noticed a slight amount of oil on one part:

You must be registered for see images attach

I would pull the shaft and inspect that u-joint more closely, there is a reason that oil is on the cross...that's the grease that's suppose to be inside, not on the outside....this would indicate the cup is maybe dry and there could be your noise.

Pull the drive shaft and move the u-joint and feel for rough movement on both sets of cups.