Rear Brake/Axle Groan...

[marin8703]

Originally Posted by JV1

I have been reading this thread for a long time now and feel it's time to jump in. We have had our H3 for over a year now (13,000 miles) and almost from the beginning the rear brakes have made the groaning noise. Seems that the RR is the worst. Wife and kids have been disgusted that I "won't take it in and get it fixed". I have never had any luck with any GM dealer being able to fix anything other than a part that was physically broken in half or a car that wasn't running. The last thing I want is to have my expensive OEM rotors turned down as a temporary fix.

My mechanical engineering background tells me the brakes aren't going to fail, they just have a systemic design flaw. I keep hearing people tied to GM stating that rear brake "groan" is inherent in the H3. That may be correct. Another correct statement is that rear brake "groan" is NOT inherent in a quality designed and manufactured vehicle. How many cars have rear brake groan? None of the fifty or so cars that I have driven in my life.

I understand the fact that these brakes were taken off some other vehicle where they performed flawlessly. I work in a high tech field where engineers do that all the time. They take a component, assembly, or system and use it on another model of the product we design and manufacture. More often than not the component, assembly, or system does not perform as it did on the original model. Why? Because the operating parameters are not the same. The temperature of the product is not the same, the RPM's are different, vibrations, oscillations, natural frequencies all are different. This would appear to be the case with the H3.

Based on what I have observed, I believe there is a problem with the front to rear balance valve (or however they get the F/R balance). The H3 literature states that the braking system is designed so that the nose does not "dive" when the brakes are applied. In my opinion the nose still dives and I see no difference from other vehicles. It seems to me that when you brake lightly, there is no rear brake action and therefore no groan. When you do medium to hard braking, there is limited force applied to the discs and therefore they grab and release, grab and release, grab and release, which gives the groaning noise.

With all these complaints, GM engineers should get off their butts and figure out what the problem is. However, if they can't fix some plastic marker lights in a year and a half, I guess there's no hope for a brake groan problem.....

, that was a good read.

[Hmmm2]

fourfourto, this is good info. After you hear what the Hummer field rep has to tell you on Jan.5, maybe you could give him JV1's thoughts, too. I think it's ridiculous for the dealers to say, "Yeah we hear it, but it must be something inherent to the H3." What?! Would we have bought it while hearing that awful sound during a test drive? Of course not. So why do we have to live with it now? I went through an awful time with the dealer last Spring/Summer. No one should have to spend that much time at a dealership with a new vehicle. THANKFULLY ... the groan has taken a hiatus (for some reason), though I cringe everytime I come to a stop .. anticipating that grind/groan sound. Good luck, fourfourto. I hope you find something out that can help us all out, too!

[fourfourto]

good info from JV1
I will mention the proportionary valve to them friday(I dont think they like my input) Not sure how to check.

It also doesnt explain how it goes away after rotors are cut and new pads installed.
The service guy would like to replace rotors and pads he just needs an ok from hummer.
Im not 100% sure that will permentaly fix the problem,Ill see on friday.

Jv1 does your noise sound like my sound files?

Hmmm3 your noise went away or you just not listening

If a H3 driven by a deaf person comes to a stop with no one around does it make a noise ?

F5 any input on the poportionary valve ?

[Hmmm2]

Originally Posted by fourfourto

:Hmmm3 your noise went away or you just not listening

LOL .. good try, fourfourto! I watch my H3 like a hawk ...nothing passes my ears or eyes when it comes to sounds, creaks, peeling A pillar mouldings, clear-coat missing from my hood, engine misfiring, stabili-trak probs, ...etc., etc. I've had a number of things wrong with my H3. Sometimes it had gotten to the point where I'd be the 3 with my son .. coming to a red light .. and I'd turn off the XM abruptly. My son would yell, "You did that just as the good part of the song was coming on!" I'd say, "Sorry, I had to listen to hear if the groan was coming back." As I had mentioned, I had heard it come back once .. sometime in September, I think. Then, not again. I would not only HEAR it, I could FEEL it in the brake pedal. It was very bad .. just about as bad as yours. I'm amazed that more people don't have the problem.

[f5fstop]

Just a note: The H3 has dynamic rear proportioning via the circuitry of the EBTCM and the lines to the front and rear brake calipers. If marketing says it will prevent the front end from diving, they are incorrect, and should be hung at dawn. Even, with NO front brakes, a sudden apply of the brakes will cause the front end of any vehicle to nosedive...something about physics.
The dynamic proportioning circuitry primarily takes effect during extremely heavy braking; a lot heavier than I hear here about the groaning noise. A lot heavier than my groaning noise that went away with a new t/case.

[fourfourto]

F5 didnt they have anti pitch /dive on the 95 to 99 Buick Riviera.
I noticed on the one I had (Great car 3.8 supercharged ahead of its time )it had a fitting on the struts to lock/dampen them during hard braking or acceleration.

[JV1]

From the H3 website:

DYNAMIC REAR PROPORTIONING
"Another integral part of this intelligent braking system is Dynamic Rear Brake Proportioning. This system modulates rear brake pressure and ensures that braking is balanced between the front and rear brakes. In English, that means that the nose of the H3 won't dive down while braking hard. And in any language, that means your passengers might not even notice what happened."

LOL - I guess they also have some other physics defying system. When the driver slams on the brakes, the nose locks so it doesn't dive and the passengers are held to their seats by a star wars invisible force field??? Who allows these people to write this stuff?

Fourfourto:
I listened to your sound files. I don't believe our H3 sounds the same but then again I've never stuck my head out the rear window to listen. Maybe I'll try it soon. With a noise as loud as yours it would seem that the mechanics ears would readily identify the major component that is generating the noise.