Weird hard braking noise

[jdrew]

Last week, Lynch replaced my transfercase planetary gears for a metal on metal clanging noise similiar to a loose brake caliper noise under deceleration from 30 to 10mph.

Now, tonight under medium braking, there is a ratcheting/grinding noise that is low pitch until the vehicle stops. (from 10-0mph) Kinda like a baseball card in a bicycle tire ratcheting noise that slows as the vehicle slows. Sounds like it is coming from the rear or middle rear of the vehicle but it's loud enough to echo off of houses on my street. Under soft braking, you dont hear it. (insert "dont brake hard" comments here.) I know of the brake rotor resurface TSB, but working around cars for a few years and knowing what type of sound that should make I really dont think that this would be my issue...

Any ideas?

[fourfourto]

It could be the brake groan, some brake lube under pads and shims seems to stop it ,(I did it myself ) it does come back though.The dealer kept telling me normal.

Link to thread

http://www.elcovaforums.com/forums/s...ht=brake+groan

F5 put this up on the X forum

Subject: Brakes Grunt, Groan, Grinding Noise from Rear When Vehicle Comes to a Stop (Refinish Rear Rotors) #07-05-23-004 - (09/26/2007)
Models: 2006-2008 HUMMER H3

Condition
Some customers may comment on a grunt, groan or grinding noise coming from the rear of the vehicle when coming to a stop.

Cause
Rotor corrosion generates a slip-stick condition transferring vibration through the suspension.

REPLACE THE ROTORS ONLY IF THE ROTOR THICKNESS IS BELOW THE MINIMUM THICKNESS SPEC AFTER REFINISH.

Refinish the rear rotors by removing 0.4 mm from both rear rotor surfaces.

Do not replace the brake pads unless the condition requires it (i.e. excessively worn, damaged, or contaminated).

If the noise persists, a brake dampening compound may be applied to the back of each pad. This allows parts to slide freely and not vibrate when moving relative to each other.

[joedirt]

Mine do it under heavy braking. It will come and go. It seems to be very common on the H3. You could always replace the front and rear rotors with the slotted and drilled rotors. The stock rotors can warp easy when offroading and driving through water. I had the same issue on my 98 Jeep Wrangler with 36" swamper tires. I replaced them with slotted and drilled rotors and never had a problem after that. I havn't tried it on my H3 yet, but I am sure that it will be better than factory. They generate less heat and do not warp easily. Someone is selling a set on ebay. Also, get some good semi metalic pads and your set. They are well worth the money especially if you have big offroad tires. Goodluck!

http://cgi.ebay.com/ebaymotors/06-07-Hummer-H3-Drilled-Slotted-Drill-Slot-Rotors-F-R_W0QQcmdZViewItemQQcategoryZ33564QQihZ019QQitemZ2 90170472834QQrdZ1QQsspagenameZWDVW

[Hmmm2]

OMG, don't remind me about that grind/groan, fourfourto. I hear it again every so often if I brake hard. I try to come to rolling stops just so I don't hear it. That ongoing fight with GM brings back bad memories. I have to admit, though ... yours was the worst I had heard.

[jdrew]

Its getting worse everyday. I'm guessing since it has been raining for the last couple of days, that could be why.... Dunno....