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Rear End Noise

  
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Rear End Noise

 
John-#010 John-#010
V-6 Camaros rule! | Posts: 44 | Joined: 04/07
Posted: 04/02/07
06:47 AM

I have a 2002 Coupe V-6 auto Camaro.  When I drive the car, a horrible warble-type of noise comes from the rear end of the car.  It is so loud that talking is difficult.

The noise starts at 10 Mph all the way up.   I have driven this car with 49,000 total miles with this noise.  Nothing really seems wrong!!

When I hang my head out the door or over the back of the car listening (at 20 Mph), it is dead silent.  Yet, you can easily hear the noise in the car.

I had the car on jacks once with engine running and wheels spinning about 40 MPH.  Again dead silent.

I have bought new tires.  I have new brakes and rotors.  I have even rotated the new tires.

I have completely disassembled my entire rear end.  I find nothing wrong.  I even put new bearings in the drive shaft.  I checked pinion gear backlash and found it about .008".  All seesm 100% normal.

What can possibly make such a deafening noise in the car, yet be undetectably outside the car??  

55Guy 55Guy
Administrator | Posts: 1153 | Joined: 07/06
Posted: 04/02/07
01:07 PM

Did you replace the u-joints? Bad u-joints can cause problems like this. Also, check the transmission. The sound may seem like it's coming from the rear, but it could be coming from the tranny.

Since you had the car in the air and heard nothing spiingin at 40 mph, it's something that's triggered when there's a driving load on the car.  

oldbogie oldbogie
V-6 Camaros rule! | Posts: 65 | Joined: 10/06
Posted: 04/02/07
03:30 PM

Is this a new noise or something that's always been there?

Bogie  

John-#010 John-#010
V-6 Camaros rule! | Posts: 44 | Joined: 04/07
Posted: 04/05/07
07:24 PM

The noise has always been there.  We bought the car used at 9500 miles.  One thought is that it could be the tranny.  I have top put it up on jacks again and try the tranny.  I hope not because trannies are expensive.

Yes, I have replaced the u-joints.  It is amazing how loud the noise is inside the car and how quiet under the car!!

John  

John-#010 John-#010
V-6 Camaros rule! | Posts: 44 | Joined: 04/07
Posted: 04/06/07
06:40 AM

Ok.  Here are some more thoughts on this mysterious noise.  Yes, I definitely want to solve it.

Let me describe the noise a little better.  It is a wobble type of noise.  If I took a guess, it sounds like the ring gear is out of round.  Like it's touching the pinion gear, then a lot of backlash on the other side.  The ring gear is not out of round because I have checked it with a dial indicator.

The noise is very constant.  I cannot load or unload it.  It is not worse up hill or downhill.  If it was inside the tranny, the noise would change as I shifted to another gear.  If it were in the ring & pinion gear, it would load and unload as I let off the throttle or gave it gas.  

I am thinking of the drive shaft.  It could be slightly out of round.  Enough out of round to cause a noise, but, no vibrations at all.  Even up to 90 Mph (which is as fast as I have ever gone in the car).  I have a second Camaro.  Both are 02 models only the second Camaro has a manual tranny.

Can I swap driveshafts between them?  Does a manual driveshaft swap with an automatic driveshaft?  Both V-6 coupes.

Since my wife drives the car 90 miles a day back and forth to work, my working time is limited.  If I knew the shafts would exchange, then I would take the time to swap them.  Otherwise, I will spend all evening trying to swap and then finding out it won't work.

John  

John-#010 John-#010
V-6 Camaros rule! | Posts: 44 | Joined: 04/07
Posted: 04/08/07
04:43 PM

Here is my decision as to what to do.  The analysis basis for my noise is two parts.  First is that there is no noise on jacks.  Nothing.  Dead silent.  Next, the noise is very speed conscious and cannot be "loaded or unloaded" in intensity.  

This eliminetes the tranny, drive shaft, and differential pinion gear.  Since the noise is constant and only under a load, it has to be in conjunction with the tires.

I have decided to replace both rear axle wheel roller bearings and seals.  I might as well replace the bearings on the ring gear since I have to go into the differential.

In some of my findings in the past, when I experience an unusual noise that can not be found easily, that noise tends to be bearings.  

I will change these out later in the month of April when the car is home so I can do it.  Since gas is back up to $3/gallon, our bicycles are now going to get more workouts anyway........John  

oldbogie oldbogie
V-6 Camaros rule! | Posts: 65 | Joined: 10/06
Posted: 04/09/07
11:09 AM

I've run into a few of these cases in different brand cars over the years and many weren't solvable because I could never pin down the source.

But at 95,000 miles you can expect things to be wearing out. You say this is speed related but not load or direction sensitive and only appears when the car is in motion but not with the driveline turning with the car on jacks.

One could consider the possibility that this is a resonant vibration between the rotating components and the body not related to anything failing just that when loaded the rotating components are at a frequency that excites the body of the car and it needs the suspension to be loaded and or a certain proximity to the ground to link these together. In that case the application of sound-deadener or insulation to body may break up the symbiotic vibration response.

Other places to look are tires, bearings and drive shaft alignment or balance, and the condition of mounts and tightness of bolts. Another is to look for broken welds, you bought this used, was it crashed?

Tires depending upon mass and tread pattern, I'm excluding balance since I figure you looked at this, can set up sympathetic vibrations with the rear end and or wheel wells. Changing brand or model of the tires could upset any resonant vibrations between these things.

Bearings are another source of speed sensitive vibrations. Some good places to look are the outboard wheel bearings on the axles. The inboards are a candidate but these and the bearings on the input pinion are pretty well lubed and don't fail anywhere near the rate of the outboard bearings, still! The transmission's output shaft is another possibility, just inside the tail shaft is a sleeve bearing that the slip yoke rides on; wear on this bearing and or the slip yoke is another possibility. A vibration or sound that changes intensity with speed is a fairly good indicator of a failing bearing.

The drive shaft, where to start, assuming you've replaced the u-joints we'll toss that. However, does the shaft run on center at all points? Are the yokes straight to the shaft and to the u-joint cups, in an up down sense the cups need to be aligned with each other both in straight ahead distance but also in twist, bent or binding yokes can set up quite a shake especially when the wheels are on the ground. What about the shaft angle? The tail shaft and the rear axle's input companion flange need to be aimed at each other with the car standing in its normally loaded condition. U-joints only work in a very small range of motion, if these parts are not aimed well the joints are forced to bind as they rotate. If the car carries a heavy load all the time whether that’s carpet samples or an (pardon me) overweight person (s) this can cause the angles between the front and rear u-joints to cause the shaft to bind. Along with this is the concept of standing heigth, has the car been lowered or raised? Have the springs sagged allowing one corner or one end to drop down. The left front is often the guilty party here as it settles under the constant load of mostly one person in the vehicle.

Failed engine or transmission mounts or loose bolts. You need to start up front at the engine mounts and work your way back checking and inspecting the engine and transmission mounts and their bolts, plus look for broken welds. The reaction link from the rear axle to the transmission get the same treatment looking for failed rubber parts, loose or missing fasteners, bends stuff like that. Same goes for the rear suspension, looking for springs that are off their mounts, missing, broken, loose bolts, rubber pads and bumpers that are ruptured, broken or missing. Same goes for the shocks.

Lastly is a careful look at the body to see if this is a rebuilt crash car. You're looking for welds that shouldn't be there, for instance a car made from two wrecks will have a weld in the floor pan the width of the car, the factory doesn't do this. You're looking for welds that have opened up, rust that has failed a weld, things like that.  

High on my candidate list is bearings, shaft alignment both front to rear and rotational and the possibility this is a car that's had major structural damage repaired at some point.

Bogie  

John-#010 John-#010
V-6 Camaros rule! | Posts: 44 | Joined: 04/07
Posted: 04/21/07
03:29 AM

I finally got to take my wife's 2002 Camaro rear axle apart.  What I found was a badly "flaked" axle on the left side.  The right axle surface also shows mild flaking.

Flakes had come off severly on the left axle.  I missed this before because I thought the axle roller bearing contacted a different part of the axle.  After measuring, I found the flaking part was where the bearing was riding.

I have 2 Camaros.  The other is a 2001.  I see a better quality machine in the 2001 than the 2002.  Maybe this is because they did not use all quailty parts as the factory was closing??

I see no "heat treating" on the axle surface.  I would expect a bear surface to be heat treated, ground, even polished.

Also, the flaking was on one side of the axle.  I am sure this is what was making my "cyclic" loud noise as I drove down the road, yet was dead silent up on jacks.

I ordered two new axles that are induction heat treated.  I also ordered new bearings, seals, and brake pads.  It's close to two weeks before I get the axles.  When it is all together and road tested, I will report back my finding.

Also, the only other possible cause of noise is the bearings in the differential housing.  I learned they are tapered.  I will take them apart and look closely for any damage.  However, I do expect that the axles are the cause.

My total cost for everything is just over $200.  I can't imagine how much cost at the Chevy dealer with them doing the work.  I am very glad that I am "mechanically inclined" so this type of repair is actually easy and fun!!

John  

55Guy 55Guy
Administrator | Posts: 1153 | Joined: 07/06
Posted: 04/24/07
01:50 PM

Yeah, some GM carriers have a bad habit of eating axle ends. The late model Chevy truck rears have the same problem. The guy who owned my '92 Silverado before me installed an Auburn carrier to solve this problem.  

John-#010 John-#010
V-6 Camaros rule! | Posts: 44 | Joined: 04/07
Posted: 05/07/07
11:18 AM

Ok, the rear end noise is now history!!  It was definitely the axles.  I ordered some new ones along with new bearings and seals. Pretty quick to install and then test.  I am so glad this noise is gone!!  

bergie60 bergie60
I love my Chevy Chevette! | Posts: 1 | Joined: 09/08
Posted: 09/05/08
07:56 PM

Hey John,
I just bought a 96 with 135K and I hear the same noise you're describing here.  Can you give me some tips on replacing the axles, bearings and seals?