ok, weird sound help please... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**jocko** · 08-16-2011, 11:53 PM

Ok, have a weird sound that seems to definitely be brake application related. My first thought was a cracked brake pad on the rear disks, but could not find any damaged pads. When applying brakes I either get a "whop whop whop" heavy rubbing sound at a frequency that is directly proportional to tire speed - or get a "clack clack clack" sound also at a frequency directly proportional to tire speed. U-joints "feel" solid front and back. (obtw, truck is an '01 silverado z71).

Before I rip this thing apart - any oddbal (or obvious) things I may be missing or should check? Extremely difficult to diagnose by myself .... i.e. have to be in the truck driving to make it happen, but it sure sounds to be coming from the left rear wheel/tire. Can hear it slightly from the right side, so that's why I checked the u-joints and checked all 4 brake pads on the rear. Could be an axle bearing I suppose, bit seems odd it's so pronounced with brake application. Sometimes, nothing at all out of the ordinary, and it all seems fine. Frustrating.

Appreciate any ideas. Sometimes it will make the noise when I'm NOT pressing the brakes - but it is VERY pronounced with brake application - so that's why I was leaning toward it being a cracked brake pad wobbling around in the caliper.

Thanks gents.

pamoffa · 08-18-2011, 09:32 PM

There is a lip on my rear dust shields that fits inside a grove in the back of the rotor, I have a 2003. This can make a scrape sound proportional to the spin of the wheel if it moved got bent or rusted out and fell apart.

donut · 08-19-2011, 10:03 AM

Are the brake pads wearing evenly? My gut reaction is bent rotor.
My 03 TB had one and did the same thing. I've had the same wump wump on the front when a caliper piston hangs up a little and won't fully release.

95 S_Trucker · 08-21-2011, 07:08 PM

look at the inside of the rotors. they are probably rusted and pitted like the moon. also check to see if the rear backing plate is rusting off

**jocko** · 08-21-2011, 08:09 PM

Thanks for all the replies gents. Found the problem - it WAS the u-joint - replaced em both. Problem solved. I was convinced it was in one of the rear brakes! Thanks again.

08-16-2011, 11:53 PM	#1
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 17,994	ok, weird sound help please... Ok, have a weird sound that seems to definitely be brake application related. My first thought was a cracked brake pad on the rear disks, but could not find any damaged pads. When applying brakes I either get a "whop whop whop" heavy rubbing sound at a frequency that is directly proportional to tire speed - or get a "clack clack clack" sound also at a frequency directly proportional to tire speed. U-joints "feel" solid front and back. (obtw, truck is an '01 silverado z71). Before I rip this thing apart - any oddbal (or obvious) things I may be missing or should check? Extremely difficult to diagnose by myself .... i.e. have to be in the truck driving to make it happen, but it sure sounds to be coming from the left rear wheel/tire. Can hear it slightly from the right side, so that's why I checked the u-joints and checked all 4 brake pads on the rear. Could be an axle bearing I suppose, bit seems odd it's so pronounced with brake application. Sometimes, nothing at all out of the ordinary, and it all seems fine. Frustrating. Appreciate any ideas. Sometimes it will make the noise when I'm NOT pressing the brakes - but it is VERY pronounced with brake application - so that's why I was leaning toward it being a cracked brake pad wobbling around in the caliper. Thanks gents.

08-18-2011, 09:32 PM	#2
pamoffa Registered User Join Date: Jun 2006 Location: massachusetts Posts: 130	Re: ok, weird sound help please... There is a lip on my rear dust shields that fits inside a grove in the back of the rotor, I have a 2003. This can make a scrape sound proportional to the spin of the wheel if it moved got bent or rusted out and fell apart.

08-19-2011, 10:03 AM	#3
donut Registered User Join Date: Aug 2009 Location: S.C. Posts: 1,593	Re: ok, weird sound help please... Are the brake pads wearing evenly? My gut reaction is bent rotor. My 03 TB had one and did the same thing. I've had the same wump wump on the front when a caliper piston hangs up a little and won't fully release. __________________ '86 C-30 dually, 454/tbh400 '73 K-20 350/350/205 (sold ) I'm kinda like duct tape- no real purpose, but handy to have around.

08-21-2011, 07:08 PM	#4
95 S_Trucker Registered User Join Date: Oct 2009 Location: . Posts: 2,187	Re: ok, weird sound help please... look at the inside of the rotors. they are probably rusted and pitted like the moon. also check to see if the rear backing plate is rusting off

08-21-2011, 08:09 PM	#5
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 17,994	Re: ok, weird sound help please... Thanks for all the replies gents. Found the problem - it WAS the u-joint - replaced em both. Problem solved. I was convinced it was in one of the rear brakes! Thanks again.



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