Need help w/front diff noise

[DAA]

I need help troubleshooting my front diff. It's a TJ Rubi 44 with the factory locker. About 56K on the whole thing, 30K on the 4.88's in it.

Can anyone tell meif there should be any play at all in a factory TJ Rubi front locker? As in, with the front wheels in the air on jack stands, I can turn one tire and the pinion rotates about 1/4 turn before the other tire starts moving. Is that kind of play normal?

Because...

I've got a noise coming from my front diff. Kind of a rubbing or low pitch bearing going bad type sound. A "ruh-ruh-ruh" sound gets faster the faster the Jeep is going. I can only hear it when coasting, but I think that might just be because with any throttle at all the motor makes too much noise to hear the sound.

With the Jeep on jackstands so the front wheels are off the ground, I can hear it when spinning a front tire by hand, although it sounds a lot different than when actually driving. Best I can describe it, is a faint, low rubbing type sound during just one part of each rotation.

But when I engaged the locker and spin a tire by hand, the noise is gone. Disengage the locker, spin a tire by had and the noise comes back. Although, like I say, it sounds a lot less obvious just turning a tire slowly by hand than it does when driving.

I just pulled the diff cover. No shavings, no chunks, not even much normal wear type stuff on the drain magnet. Fluid smells good, ring and pinion look great etc. I can't see anything obviously broken or out of place.

Any help with troubleshooting from here would be greatly appreciated.

A little background that might help... First noticed the noise coming home from The Swell ago and I did use the front locker a couple times that day.

The first thing I checked, was disconnecting the front driveline and going for a drive. The noise was still there. The next thing I checked, was my unit bearings - and they were BAD. One of them was totally wasted and the other was just pretty bad. So I was sure I had found the problem/source of the noise. Replaced the unit bearings, first test drive, no sound, thought I was golden. Went for about a 200 mile drive yesterday and started hearing the sound again, intermittently. By the time I got home, it was back the same as it had been before - could hear it plain every time I'm coasting.
So, the unit bearings definitely needed replacing, big time, but that's not what I'm chasing I guess. Between the drive home from The Swell when I first noticed the noise and yesterday's trip up to the Uintas, I have driven a bit over 400 miles and I can't really say for sure if it is getting any worse or not, but I think it is.

- DAA

 

[TJDukit]

Even though it may not be the culprit make sure you check your u-joints on the shafts really well. When my unit bearings went out on my last TJ they cooked my u-joints and I almost missed it.

 

[DAA]

I should have mentioned that, but I forgot. I did replace the front axle u-joints at the same time as the unit bearings - the old ones had one dry cap each (figures...).

- DAA

 

[RockChucker]

Is the TJ front Rubicon 44 a Limited slip type like I am pretty sure the rear is? And isn't it a gear type like a Detroit Truetrack? Or am I way off here? Could it be gear noise in the locker itself? Have you pulled the cover and spun it while it is off the ground like you have done before? That way you can see what is going on, and if it is noise in the diff, I would think it would be louder and more pronounced.

What brand unit bearings did you get? Could one or both possibly be toasted already?

 

[jeep-N-montero]

I know that if a unit bearing is bad enough it can cause some uneven brake wear, did you check your wear patterns on the pads and rotors and see if there is any rubbing? Lubed the caliper slider pins lately?

 

[DAA]

The front TJ Rubi locker is open when not locked - and I do have the cover off it with the wheels in the air right now. Everyting I can see, looks fine (but I'm not all that sure what a Rubi locker "should" look like...). Spinning it by hand, I can hear it with the cover off, but still can't pin point the source. Could be inside the locker, could be a pinion bearing maybe? Really don't know. Put factory unit bearings from the dealer on it, already pulled them back off for inspection, they seem as tight and right as can be.

Brakes are looking great too and the noise really seems to be coming from the diff, not the ends, although, to be honest, since I can't pin point it, I can't be sure.

- DAA

 

[rholbrook]

They make a stethoscope with a tube on it that you could use to touch the bearings with as you have someone spin it. You could also put it close to the locker too and where it may be coming from. Someone local has to have one you could use for a few minutes. I used one to find a bad pulley and they work slick.

I am out of town for a few weeks but if you can't find one let me know and I will have my son come by with one and he can spin the tires for you while you poke around and listen

 

[DAA]

Thanks Russ. I used a screwdriver in my ear on the diff cover before pulling it (handle end in ear, tip against diff cover). Doesn't work near as well as an actual stethoscope I'm sure, but better than the naked ear. Haven't tried it on a bearing or anything since taking the cover off though.

- DAA

 

[DAA]

Okay, just trying to think this through out loud here…

IF I’m putting the source of the sound in the right place and it really is coming from somewhere in the diff, and…

IF the sound really goes away when the locker is engaged, then…

IT has to be something in the locker itself, doesn’t it? A pinion or carrier bearing wouldn’t get quiet just because a locker is engaged, right?

I’m not familiar with this locker at all. It seems strange to me that it could have something broken or damaged to the point it makes an unhealthy sound, yet it still engages and disengages, works just fine and no chunks or metal dust in the oil at all. But, maybe so?

Later today I think I’ll put the cover back on and put some gear oil in there and take another test drive and try engaging the locker to see if the sound really does stop with it engaged. Won’t have the patience to let RTV setup properly so it will probably leak and I hate to waste expensive gear oil so I’ll probably just put 1 qt of straight 90W in it just for a short test drive.

- DAA

 

[driver920]

well in my opion and from my experiance yes it would change the noise if it is coming from the center section because you are changing the pressure on it when you engage and dissengage the locker more likely with a carrier side bearing than a pinion bearing but i agree with the stethescope but what i may do would be remove the rear driveline block weels front and back jack up the front put on stands MAKE SURE IT IS SECURE put it in low range first gear and let it rotate and start listening with said stethescope at every bearing intersection in and on the housing and maybe even grease the front driveline u joints if you havent already slight sounds on a part just starting to wear out can be a pain to find and the can travel from very unsuspecting places

 

[Hickey]

Check that driveline too. They can make a lot of noise when the cv wears out.

 

[bryson]

The noise you are hearing with the cover off and the Jeep in the air could just be the side gears and spider gears in the locker... The spider gears stop turning when the locker is engaged, hence the noise going away when its locked. I don't think it is terribly abnormal for them to make a little bit of noise in this situation - especially with no oil. I would guess that the noise you are hearing while driving, and this noise are NOT the same noise.

Think about it this way... when you are driving straight, both front tires turning, there are zero internal parts in your locker that are moving. It doesn't matter if your locker is locked or unlocked until you turn the steering wheel.

To truly duplicate your issue on jack stands, you would have to turn both tires at the same time - whether you accomplish this by locking the locker and turning one tire, or unlocking it and having a helper turn the other tire shouldn't matter.

Are you sure the seal didn't get smacked on a rock or something to the point where the dust shield is rubbing on the pinion yoke? Could it be the front output bearing in the t-case? You said it still makes noise with the d-line out, but Hickey is wise, and the CV is still a good point to check.

Not 100% sure, but I think the TJ rubi lockers have a switch in the diff (threaded into the housing) to tell the ECM if the locker is locked or unlocked... Is it possible that this switch is rubbing on something and making your noise?

 

[DAA]

Lots of good thinking flowing here, I appreciate it.

Driver920, I follow you about the locker possibly quieting a bearing noise. I just picked up a cheap stethoscope from O'Reillys, and will probably end up with the whole Jeep up on jackstands and the wheels turning in 4WD tonight.

Check that driveline too. They can make a lot of noise when the cv wears out.

That was my first thought. But, on a test drive with the front driveline disconnected, the noise was still there.

I don't think it is terribly abnormal for them to make a little bit of noise in this situation - especially with no oil. I would guess that the noise you are hearing while driving, and this noise are NOT the same noise.

This makes sense. And I'm half afraid you are right. NOT that I'm anxious to have to spend the bucks on replacing a locker, just that I AM anxious to find out exactly what the issue is so I can get it fixed. But, yeah, I can feel and hear "something" when spinning tires by hand on jack stands. But I'm not totally convinced it's the same noise I'm hearing while driving yet either. I just want it to be, so I can get this thing nailed down and put to bed. But, really, my hearing is so bad, and the way a noise can travel through steel, I wouldn't be shocked to find out it's not even coming from my front axle, when all is said and done. As of right now though, that front diff is still my prime suspect.

Are you sure the seal didn't get smacked on a rock or something to the point where the dust shield is rubbing on the pinion yoke? Could it be the front output bearing in the t-case? You said it still makes noise with the d-line out, but Hickey is wise, and the CV is still a good point to check.

Not 100% sure, but I think the TJ rubi lockers have a switch in the diff (threaded into the housing) to tell the ECM if the locker is locked or unlocked... Is it possible that this switch is rubbing on something and making your noise?

This is all possible and I haven't thought of/checked/ruled out any of it yet. I'll try and look at all of these items later today. And I think before putting the cover back on the diff or taking another test drive, I'll pull all four tires so I don't have to get the Jeep up so high and put it on four jack stands and run it - see if I can hear the noise at all and if I can, maybe get a better idea EXACTLY where it is coming from. And if it is coming from the diff like I think, maybe the stethoscope can help me narrow it down further.

Thanks fellas.

- DAA

 

[rholbrook]

Dont let Cindy behind the wheel while your checking it. Too tempting for her. It drives my wife nuts when I go looking for sounds, she says how can I hear strange noises when I can't even hear her. I won't get into obvious reasons for that but I heard the belt pulley on my Expedition a month before she did. Just turn the radio up is my wife's solution.

 

[sixstringsteve]

It drives my wife nuts when I go looking for sounds, she says how can I hear strange noises when I can't even hear her. I won't get into obvious reasons for that but I heard the belt pulley on my Expedition a month before she did. Just turn the radio up is my wife's solution.

 

[DAA]

Cindy was with me the first time I noticed it, coming home from The Swell, and she was with me when we heard it again heading up to the Uintas the other day. I'm glad she was, so she doesn't think I'm just making up excuses to pour money into the Jeep. She gets these crazy notions in her head about this kind of stuff, I don't know why...

- DAA

 

[DAA]

Update...

I tried listening with a stethescope while spinning front tires by hand. I could hear what I think I'm hearing in the diff, but couldn't pin point it. If anything, it might have sounded a bit more distinct at the carrier bearing caps than the pinion housing, but neither location really rang out as a clear source. Definitely though, the sound I hear and feel while spinning front tires by hand was there in the 'scope.

Next I got the Jeep up on jack stands (with no wheels), put it in 4Hi and let it run. Between the motor noise, exhaust, fan, and drivetrain, I had so many noises coming from so many directions it was just kind of confusing. Once I put it in 3rd gear though, I started hearing a very distinct rotational knocking kind of noise. Like an amplified version of what I hear spinning front tires by hand - not so much the ruh-ruh-ruh noise I get while driving. But, even as loud and distinct as it was, and using the stethoscope, I'll be damned if I could pin point the source. It sounded loudest at the rear t-case output and at the pinion - I couldn't safely reach the front t-case output with the driveshaft spinning. At the rear output and pinion, same sound, about the same loudness, just different texture. I honestly couldn't tell if it was originating from one end or the other or somewhere in the middle.

Next I engaged the front locker to see what that would do the noises I was hearing. Holy crap did that make a LOT of noise! Lots of heavy metalic clanking sounded like it was coming from one end of the front axle then the other. It was so loud it was drowning out everything else. I think it was just the small slop in the locker being taken up and clanking as one axle shaft took power, then as the play went out of that side the other would clank as it took power and just kept doing that back and forth over and over. In other words, I "think" all that racket was normal under the circumstances. If not, then maybe I'm just whiffing right past a big clue to the real problem?

So... Now I'm not at all sure it's even front axle - maybe it's t-case output or even rear drive shaft. So...

I put the tires back on, the diff cover back on and a qt. of gear lube inside. Then I pulled the rear drive shaft, put it in 4Hi and went for a test drive. Definitely, the noise is NOT coming from the rear drive shaft! In 4Hi with no rear drive shaft, the noise is louder and more defined than ever. For the first time, I am easily hearing it while the motor is under load. Up till now, I could only hear it while coasting. I thought that was probably only because I couldn't hear it over the motor noise with any throttle, not because it was only making noise while coasting. Now I know for sure it sounds off all the time. And I also know it definitely gets louder when running on only the front axle. Which is probably a clue, but, to what exactly, I don't know...

And that is where I sit now. After dinner I may try another test drive to try and make a sound recording of the noise before I put the rear shaft back in. Next up I guess will be disconnecting the front shaft again, just to double check and be thorough.

I hate chasing ghosts like this. I would have rather opened the diff and found busted stuff staring me in the face than be chasing my tail like this...

- DAA

 

[DAA]

Okay, made a quick video clip of driving it with the rear drive shaft removed, on only the front drive shaft in 4Hi. The noise came through loud and clear in the video.

[video]http://www.youtube.com/embed/cAQOOOuCsI8[/video]

After shooting that video clip, I put the rear drive shaft back in and disconnected the front again and took another test drive. Noise is definitely still there. Although, no doubt, the sound is definitely more pronounced, louder and angier when driving on the front axle than the rear.

So, I think I'm back where I started. Pretty sure it's in the front diff, but don't know if it's a bearing or the spider gears or the locker.

- DAA

 

[RockChucker]

It is pretty hard to tell what the noise is from the video. To me it almost sounded like tire noise, but I am sure it is not. My dad's Jeep was making a similar rhythmic noise like that when in 4 low, and it turns out the tcase chain had stretched and was dragging across the bottom of the case.

PS...if you are going to be removing the diff covers multiple times during this project, which it sounds like you may, why not invest in some lube locker reuseable gaskets? I have never used them myself, but I have heard good things about them.

 

[Hickey]

I'm feeling t-case.