I heard a noise today.....

[gmcman]

Was not a pleasant sounding noise either.

I'm hoping it's nothing to worry about but here's what happened....long but bear with me.


Keep in mind I now have the SS rear with the limited-slip.

I dropped the kids off at daycare this morning, when I pulled into the parking lot, I pulled past the spot and spot is on the right... then backed in. I did straighten out for a few feet and backed straight for about 3-4 feet and not solely on a turn.

When I went to leave and when I always pull away, same thing...business as usual, same for 10 years in this vehicle... I apply the brake, pull the shifter down to "D", then wait for about a second for the tranny to engage then pull away. This time however and likely being in a rush, I "thought" the tranny engaged and I believe simultaneously just before the trans engaged I touched the gas.

Now, I don't think the RPM's climbed over 1200 but still there wasn't positive engagement when I tapped the gas but nonetheless, when the trans engaged there was an awful sound,....CLACK, CLACK, CLACK... my first thought was the rear stripped out but there's no way under such light throttle. Almost sounded like you grabbed "PARK" with the wheels rolling slightly and there is that horrendous clicking sound until the tires stop but this was twice in intensity and sounded like about 2-4 rapid clicks.

Then I thought I stripped the sunshell but I drove it 30 miles to and 30 miles back home....no issues and no noises. I then thought I may have dragged the hitch on the curb so before I went home I went back to the parking lot and there is a fresh dig in the curb but appeared to be over a foot from where I was but my gut tells me it wasn't a dragging sound.

So my thoughts are.....

1. Possibly the clutches disengaging in the rear.

2. What is in the transfer case that when in 2WD could cause such a noise.

3. Perhaps trans or rear end clutches slipping slightly and the noise was driveline lash slapping back and forth.

Hard to say but it was a very pronounced, sharp, metallic noise and I thought I was going to be parked there for awhile....luckily nothing...so far.

 

[Sparky]

Maybe this isn't the best thing to do, but if it were me I'd just smack myself for moving too fast and just go about my business as long as the truck is acting fine

 

[CaptainXL]

I heard a CLACK, CLACK, CLACK...

That's exactly the type of sound I get at times when my G80 is locking up. If you were up on a curb then the other wheel was probably in the air which caused it to engage. Nothing to worry about.

 

[gmcman]

That's exactly the type of sound I get at times when my G80 is locking up. If you were up on a curb then the other wheel was probably in the air which caused it to engage. Nothing to worry about.

No, wasn't on a curb. I was in the spot normally, the hitch ball bolt may have dragged the curb since it was hanging down but the tires were in front of the curb.

The SS rear has LSD, does not have the G80.

 

[CaptainXL]

No, wasn't on a curb. I was in the spot normally, the hitch ball bolt may have dragged the curb since it was hanging down but the tires were in front of the curb.

The SS rear has LSD, does not have the G80.

Might also have a G80 in it as well. Have you checked? Maybe the person you got it from decided to do some rock climbing or something and switched it out?

 

[Denali n DOO]

Might also have a G80 in it as well. Have you checked? Maybe the person you got it from decided to do some rock climbing or something and switched it out?

For me as soon as I hear that "click click click" of the G80 locking then my traction control light goes off and I then know it was the G80 locker making the noise.

 

[CaptainXL]

Well it's not so much a click. Its more of a bang/clunk for me. lol. I think mine is getting worn out and it just slams into lockup. Maybe I need to add some whale oil or something.

 

[Denali n DOO]

Well it's not so much a click. Its more of a bang/clunk for me. lol. I think mine is getting worn out and it just slams into lockup. Maybe I need to add some whale oil or something.

Your right, it is more of a clunk than a click...

 

[HARDTRAILZ]

Pull the diff cover...sounds like spider gears and since you said the axles were bent before they probably were worn and just putting in new shafts did not fix it. It probably amplified the wear and moved the wear pattern, possibly to a weak spot and could have easily led to failure.

I have a spare g86 out of my SS rear from putting in the locker. Complete with carrier because the locker required the stronger open carrier.

You really should pull the cover and at least look. If the spiders are busted and pieces are floating around you may ruined your gears pretty quick if the teeth are not busted too.

 

[HARDTRAILZ]

That's exactly the type of sound I get at times when my G80 is locking up. If you were up on a curb then the other wheel was probably in the air which caused it to engage. Nothing to worry about.

I would be checking your G80. They are not supposed to make noise. Should be an almost smooth event not something that grabs your attention or you hear.

Might also have a G80 in it as well. Have you checked? Maybe the person you got it from decided to do some rock climbing or something and switched it out?

Be pretty pointless to do a G80 when they are not really designed for or strong enough for that. For the cost, most would do a locker.

For me as soon as I hear that "click click click" of the G80 locking then my traction control light goes off and I then know it was the G80 locker making the noise.

I dont think I ever heard my G80 engaging, esp not a click click sound. Maybe a little pop when a tire would slow down and allow engagement, but a clicking would indicate something is not right. Have you had your cover off and checked it out?

 

[CaptainXL]

I would be checking your G80. They are not supposed to make noise. Should be an almost smooth event not something that grabs your attention or you hear.

I disagree wholeheartedly. Every new leased truck I have had with a G80 makes a clunk noise when engaging. The manual even states that you shouldnt worry about the clunk. My last truck was a 2008 GMC Canyon with the I5 and it made the same clunking noise burning rubber out the dealers lot.

I wish I had traction bars or a hop shock on that thing. The wheel hop was pretty bad. But if given enough pedal it would straighten up and burn rubber even in second gear. It was a fun sporty truck.

 

[HARDTRAILZ]

I disagree wholeheartedly. Every new leased truck I have had with a G80 makes a clunk noise when engaging. The manual even states that you shouldnt worry about the clunk. My last truck was a 2008 GMC Canyon with the I5 and it made the same clunking noise burning rubber out the dealers lot.

I wish I had traction bars or a hop shock on that thing. The wheel hop was pretty bad. But if given enough pedal it would straighten up and burn rubber even in second gear. It was a fun sporty truck.

One clunk/pop to engage I get, but if it is doing it more than that; it is engaging and diengaging or is broke. With a burnout, I get that because the G80 releases at a certain speed...20 mph maybe... so it could engage and re-engage as wheel speed and traction differ.

I have owned g80's across a variety of platforms for nearly 20 years and not had one that was good make multiple clunking noises and definitely not do that all the time. I had some g80's last for 5 years and others I would destroy easily. I have babied them and blown pieces through diff covers. The worst was a cold morning in a camaro and at 2000 rpm the shift kit popped it into second with very little throttle and the g80 disintergrated and locked up the rearend. I have had tires spinning from the mud to pavement to mud to rocks and had them hold up. Seems to just be dumb luck when they break, but far too often they do break.

I worked the shit out of my G80 offroad and when I had one wheel spinning I would have to feather the throttle to get the g80 to engage and it would make a light thunk as it locked in, but once in it would just work and be silent. If it is locked...there is nothing to click or clunk or pop.

 

[CaptainXL]

One clunk/pop to engage I get, but if it is doing it more than that; it is engaging and diengaging or is broke. With a burnout, I get that because the G80 releases at a certain speed...20 mph maybe... so it could engage and re-engage as wheel speed and traction differ.

I agree with all that you said except for the above. ..

The lockup mechanism won't disengage above 20 MPH if you are already locked up starting under 20 MPH. It doesn't go by vehicle speed anyway. It works by way of the driveshaft rotation. You can lock it up and go 40 MPH if you want to. Granted you will be limited to a straight line because it will lockup and act like a spool.

Overall though. Yes, if you are engaging and disengaging when it shouldn't then you could have a problem. It's difficult to say though. You would need a camera pointed at the wheel or peel out marks on a dirt road to see if the wheels are both locked when they should be.

The fact is that it does make noise and it's normal. The fact that it can make a clunk, clunk, clunk three times or more says nothing about how it operates correctly. In fact it could just be a loss and immediate regain of traction. It works pretty fast if your right at the 20 MPH limit.

 

[HARDTRAILZ]

The lockup mechanism won't disengage above 20 MPH if you are already locked up starting under 20 MPH. It doesn't go by vehicle speed anyway. It works by way of the driveshaft rotation. You can lock it up and go 40 MPH if you want to. Granted you will be limited to a straight line because it will lockup and act like a spool.

Good to know, but...
Why a straight line...you can turn with a spool, especially with tires spinning? The front is free to act as it wants. I turn all the time with my locker engaged. The tires just chirp a bit.

The fact is that it does make noise and it's normal. The fact that it can make a clunk, clunk, clunk three times or more says nothing about how it operates correctly. In fact it could just be a loss and immediate regain of traction. It works pretty fast if your right at the 20 MPH limit.

But he was not at 20...he was in a parking lot barely moving with no traction issues. He also bought the rearend and it came with bent axle shafts. He got newer shafts but they were not perfect either. Quite logical that the bent shafts could have harmed the LS in the rearend and he should pop the cover and take a look.

 

[Denali n DOO]

 

[CaptainXL]

Good to know, but...
Why a straight line...you can turn with a spool, especially with tires spinning? The front is free to act as it wants. I turn all the time with my locker engaged. The tires just chirp a bit.

It is the natural tendency of the vehicle to want to go straight when locked up. When I locked it up I usually wasn't on a dirt road or rocks like you do. So I would rather not press my luck hurting anything on pavement. Which reminds me, we are kind of getting off track here.

But he was not at 20...he was in a parking lot barely moving with no traction issues.

Could be oil on the ground? Who knows.

 

[HARDTRAILZ]

It is the natural tendency of the vehicle to want to go straight when locked up. When I locked it up I usually wasn't on a dirt road or rocks like you do. So I would rather not press my luck hurting anything on pavement. Which reminds me, we are kind of getting off track here.

I drive on pavement 90% of the time and have a locker that locks in with just about any throttle application. It does not push the truck on pavement nearly like it does offroad; where the front tires have less grip. On pavement the rear tire is more likely to slip than have the truck pushed in a straight line. I dont see it as pressing any luck to drive with the rear locked. I have had several vehicles locked in the rear, but what do I know...

 

[The_Roadie]

The lockup mechanism won't disengage above 20 MPH if you are already locked up starting under 20 MPH.

That's my understanding. I wouldn't be rock crawling as fast as 20 MPH, but my study of the Eaton theory of operation hints that the pawls won't disengage and allow the clutch plates to cam apart unless torque is released and the throttle backed off a bit. A subtle point in this discussion about noise, however.

One clunk/pop to engage I get, ... I worked the shit out of my G80 offroad and when I had one wheel spinning I would have to feather the throttle to get the g80 to engage and it would make a light thunk as it locked in, but once in it would just work and be silent. If it is locked...there is nothing to click or clunk or pop.

This is also my experience. The only G80 I broke was an 8" during a snow extraction when I overestimated its robustness. Dumb move. Cost a couple of $$ to get home and fixed. On the trails, I ALWAYS feather the throttle to prevent a high RPM engagement. Especially with more rotating mass than the designers intended to be hanging off the axle.

But he was not at 20...he was in a parking lot barely moving with no traction issues. He also bought the rearend and it came with bent axle shafts. He got newer shafts but they were not perfect either. Quite logical that the bent shafts could have harmed the LS in the rearend and he should pop the cover and take a look.

The only time I had a multiple clunk was when parts broke, and I was generating what one member called the "fine grind" inside (and some through the cover) of the diff.

 

[CaptainXL]

I dont see it as pressing any luck to drive with the rear locked.

Im strickly talking about the G80. I can't comment on any type of spool or locker that you might have.

Let me explain. ..

In the case of a G80 were the ramp up feature partially engages as wheel speed differs you can normally hear it chatter when turning. This is the G80 partially engaging and releasing. This is normal. I have also had a few cases where the G80 stayed in full lock while turning even after coming out of an accel. According to the service manual you backup a few times and do a bunch of 360 turns in both directions to unstick the clutch pads.

All I know is that the wheels hopped like crazy when the rear was locked coming out of some of those runs. It just didn't feel good at all as I was dragging the tires. I could feel the strain being placed on the driveline while turning. To me that is pressing my luck considering the limited strength of the side and spider gears in these things.

Bill's explaination of the working parts is excellent. I wish I could remember all those part names. But at least it appears we understand the workings of it enough.

 

[HARDTRAILZ]

I know how a G80 works. http://gmtnation.com/f79/how-g-80-works-1510/

I also know out of the dozen or so I have had, none chattered and clunked multiple times as you keep stating yours do. I never heard noises other than the initial lock.

 

[CaptainXL]

I know how a G80 works. http://gmtnation.com/f79/how-g-80-works-1510/

I also know out of the dozen or so I have had, none chattered and clunked multiple times as you keep stating yours do. I never heard noises other than the initial lock.

I am not disagreeing with what you say. And it's great you never have noise. But I have found that chattering is normal. You can try to get rid of the noise using different fluids and stuff but sometimes chatter is still there. It's in the owners manual.

Everything I said is true. If you have a problem with my description I can direct you to some engineering folks over at Eaton. I have a couple of their numbers as I used to work there a few years ago.

 

[HARDTRAILZ]

Bullshit man. Chattering is normal. Where are you getting this from?

Everything I said is true. If you have a problem with it I can direct you to some engineering folks over at Eaton. I have a couple of their numbers as I used to work there a few years ago.

I am getting it from real life experience. Why would something locked together chatter?

Chatter is due to crud in the plates or using a fluid with a friction modifier and should be resolved by changing the fluid per GM service bullitens I read awhile back.

 

[HARDTRAILZ]

--------------------------------------------------------------------------
Service Information 2007 Chevrolet TrailBlazer - 4WD | Envoy, Rainier, TrailBlazer, Ascender VIN S/T Service Manual | Bulletins By Category | | Document ID: 2505329 --------------------------------------------------------------------------------

#PIP4054D: Eaton Locking Differential Chatter Shudder Noise On Turns - (Jul 19, 2010)


Subject: Eaton Locking Differential Chatter Shudder Noise on Turns


Models: 2004-2007 Buick Rainier

2000-2011 Cadillac Escalade, ESV, EXT

2002-2011 Chevrolet Avalanche

2004-2011 Chevrolet Colorado

2003-2009 Chevrolet Express

2000-2011 Chevrolet Suburban, Tahoe

2000-2007 Chevrolet Silverado Classic

2007-2011 Chevrolet Silverado

2002-2009 Chevrolet Trailblazer

2004-2011 GMC Canyon

2002-2009 GMC Envoy

2000-2011 GMC Yukon, Yukon Denali, Yukon XL

2000-2007 GMC Sierra Classic

2007-2011 GMC Sierra

2003-2011 GMC Savana

Equipped With a Locking Rear Differential RPO G80




--------------------------------------------------------------------------------

This PI was superseded to update model years. Please discard PIP4054C.


--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Customers may comment on a chatter or shudder from the rear axle on vehicles equipped with an Eaton locking differential. This condition would be noticed in parking lot maneuvers, turning, or during locking differential engagement and may be more noticeable when the differential is hot. Locking differential clutch chatter may be causing this concern.

Notice: This does not apply to vehicles equipped with RPO QS4 (Quadrasteer) which is part of option package NYS. Quadrasteer vehicles use Dana axles and have a different fluid requirement.

Notice: This PI does not apply to vehicles equipped with a RPO G86 limited slip differential.

Recommendation/Instructions:
If differential clutch chatter is encountered in a vehicle equipped with an Eaton locking differential, flush, drain and refill the differential with new synthetic fluid, use the fluid part number listed in SI for the vehicle currently being worked on. If the condition returns, replace the rear differential clutch This PI was superseded to update model years. Please discard PIP4054C. plates and refill the differential with new synthetic fluid, use the fluid part number listed in SI for the vehicle currently being worked on. Refer to eSI for clutch plate replacement and set up procedures.

Notice: Eaton locking differentials used in 10.5[Prime ] rear axles are equipped with steel clutch plates. It is a design characteristic of these steel clutch plates to exhibit more clutch chatter than other models.

Important: Installing any friction modifier causes the clutch pack in the locking differential to slip and miss engagement. A fluid flush can often remove debris that is a contributor to clutch chatter. Adding friction modifier additive can cause a loss of locking differential functionality.

Notice: On Quadrasteer equipped vehicles, simply flush the rear axle and refill with the fluid listed in SI document 793720 under the steerable application.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


© 2010 General Motors. All rights reserved.

 

[CaptainXL]

I am getting it from real life experience. Why would something locked together chatter?

Chatter is due to crud in the plates or using a fluid with a friction modifier

Yes, as in NEW vehicle has a G80 and the plates/need to be broken in. Perhaps thats where we see a disconnect. I have always seen this exhibited in new vehicles. Perhaps you are describing the G80 after..oh say 50,000 miles? Could that be it?

And the presence of any friction material between plates can easily be removed by repeated actuation of the locker. It is in a fluid environment with a magnet. So any metalic material would eventually find it's way to it. And that's why it's important to drain and fill a G80 after the first 500 miles.

 

[HARDTRAILZ]

Not noticed in a NEW Silverado and S series Blazer.....


But there is a breakin period on all new rearends. There is when adding a locker or changing gears, but it is not typical for a G80 to chatter after the Standard break-in. Every rearend whether posi, locked, open, 3.42, 4.56, 5.13, gm, ford, jeep goes through a break-in and acts non-typical.

What G-80 brand new right off the lot is NOT what a G80 truly acts or preforms like. It needs broke in and seviced and they specifically say not to run them hard in this break-in period and not to get them hot.

If you really did a burnout leaving in a new truck...that is your own stupidity. I would not be surprised if your G80 never got properly broken-in and always made noise.

 

[CaptainXL]

Not sure why you pulled that tsb up?

That's to resolve customer complaints about extreme shudder. Not what I am talking about here at all.

In fact if you look down a bit GM actually admits that some chatter is normal on 10.5 inch as well as some on all others.

I highly doubt that my clutch packs need to be replaced pulling out of a dealer parking lot. lol

 

[gmcman]

You really should pull the cover and at least look.

So what better things to do at 9PM in the driveway.....

As soon as I made it home I drained the rear and pulled the cover...I wasn't going to sleep well unless I checked it out. Turns out everything checks out and I cannot see anything out of place. I had the wifey feather the brake while one tire was on the ground and I watched all the gears and all looks good.

I went as far as attaching a dial gauge and ran it along the ring gear and any smooth surface I could and there was absolutely zero movement on the dial which was reassuring.

I do feel alot better now for the most part, glad I did take a look. Here's a pic of the inside as of tonight.

I have a pinion seal leak though...not running out but not weeping either, kinda in between. As long as the rear sat outside I'm not surprised.

Can I change the seal and reuse the crush sleeve?

 

[Sparky]

How long have you had it in there?

When I first put my junkyard axle in the pinion seal blew oil rather horribly. I was really mad at this point (long story on the axle history, though you may remember my rant on the OS about it), so I just topped it off until I could decide what to do about it. It stopped leaking by itself, and the pumpkin is still full. Almost like the seal was dry and shrunk a bit, but after use and lubrication it sealed back up again.

Maybe just run it for a little while and see how it does. Yours may do the same.

 

[gmcman]

So far about 600 miles.

I'll give it a little more time I suppose, unfortunately this fluid is expensive...don't want to leak too much.

 

[gmcman]

On occasion the "thunk" is stronger than what's in these audio clips but here's what I'm getting right now. Sorry for the sound quality but I recorded this on my cell on my way home. The noise is when I either roll to a stop or go from "D" to "R" and lightly stab the gas.

I want to speculate that without the yoke being greased that could be the culprit but it's a healthy noise.

 

[gmcman]

I crawled under and looked for broken or loose pieces and all was intact. I pulled the driveshaft to grease the yoke and checked all the control arm bolts in the process.

Three bolts were loose enough to surely not be able to contain the massive torque from the I6

Tightened all to 97 ft/lbs and 2 were actually pretty loose, I tightened them initially so I will keep an eye on them. Could have overlooked them, dunno but will give it a test here shortly and report back.

 

[gmcman]

Well, all is good...nice and quiet. :wootwoot:

Obviously an error on my part but thankfully it's fixed. Barely any noise from R to D to R and the grease really took alot of the noise from the driveline.