Noise from undercarrige

gss036 · September 7, 2005

I started getting a noise about a month ago. I come off a flat road way, few bumps, the turn right into a "C" turn and start up an incline of about 20 degrees and I get this errrrrrr noise. I try to do the same thing again, can't get a repeat. Several days later at the same place here the noise is again. I have read several posts about noises? Would this be from my posi-traction rear end or the anti-lock brakes trying to activate? I talked w/service rep at dealer, of course his answer is leave the truck and lket them check it out. OK no noise what are they going to find?

chevy4x4trucks · September 7, 2005

the posi will make a sort of clunk noise when it engages... which it usually does on sharp turns, especially up inclines.

think of the sound as a ball bearing rolling and hitting a metal wall

gss036 · September 7, 2005

the posi will make a sort of clunk noise when it engages... which it usually does on sharp turns, especially up inclines.

think of the sound as a ball bearing rolling and hitting a metal wall

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I spoke with a mechanic friend (30 yrs exp) and he suggested I put in a small bottle of the Ford lube stuff for locking rear ends. The parts guy who has been at the Ford garage for the past 35 yrs, says he sells a lot if it for the GM products. I bought a bottle and put it in, so will see if that makes any difference. Sure does stink though!

This truck has only got 39500 miles on it, engine was rebuilt at 11000 and replaced at 15000 miles and I haven't had any problems since, so hope to keep it several more years.

scottlambson · September 8, 2005

Do you have the G80 RPO code? Most 99 Z-71's don't have the limitied slip rear end. Mine doesn't although I wish it did.

Could you describe the 'errrrr' noise. When I make the noise out loud it sounds like squeeling tires.

gss036 · September 8, 2005

Do you have the G80 RPO code? Most 99 Z-71's don't have the limitied slip rear end. Mine doesn't although I wish it did.

Could you describe the 'errrrr' noise. When I make the noise out loud it sounds like squeeling tires.

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The noise sounds more like the rear disc brakes grabbing with a pieces of rock chip or something stuck between the pad and the rotor. I can look at the rotors and they are not gouged , but not a smooth wear like you would expect. It doesn't happen often enough to really listen and comes as a surprise and then it's gone again. That is what makes it tough to figure out.

Yes, I do have the G80. I have the line sheet from the Ft Wayne assy plant and it is listed under the options list. I wish I kenw what all the numbers meant, but probable just factiry codes for assebly line parts installed.

gss036 · September 15, 2005

Do you have the G80 RPO code? Most 99 Z-71's don't have the limitied slip rear end. Mine doesn't although I wish it did.

Could you describe the 'errrrr' noise. When I make the noise out loud it sounds like squeeling tires.

<{POST_SNAPBACK}>

The noise sounds more like the rear disc brakes grabbing with a pieces of rock chip or something stuck between the pad and the rotor. I can look at the rotors and they are not gouged , but not a smooth wear like you would expect. It doesn't happen often enough to really listen and comes as a surprise and then it's gone again. That is what makes it tough to figure out.

Yes, I do have the G80. I have the line sheet from the Ft Wayne assy plant and it is listed under the options list. I wish I kenw what all the numbers meant, but probable just factiry codes for assebly line parts installed.

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Well, it has been a week since I put the rear additive in and spun the wheels real good on a gravel road and showed good lock up and I haven't had any more strange noises, but have only been back over the curve/hill once since then. Hopefully the problem is solved.

Added 9-19-05 I have gone back over the same spot 3-4 more time s and no more noises.

gss036 · October 31, 2005

Do you have the G80 RPO code? Most 99 Z-71's don't have the limitied slip rear end. Mine doesn't although I wish it did.

Could you describe the 'errrrr' noise. When I make the noise out loud it sounds like squeeling tires.

<{POST_SNAPBACK}>

The noise sounds more like the rear disc brakes grabbing with a pieces of rock chip or something stuck between the pad and the rotor. I can look at the rotors and they are not gouged , but not a smooth wear like you would expect. It doesn't happen often enough to really listen and comes as a surprise and then it's gone again. That is what makes it tough to figure out.

Yes, I do have the G80. I have the line sheet from the Ft Wayne assy plant and it is listed under the options list. I wish I kenw what all the numbers meant, but probable just factiry codes for assebly line parts installed.

<{POST_SNAPBACK}>

Well, it has been a week since I put the rear additive in and spun the wheels real good on a gravel road and showed good lock up and I haven't had any more strange noises, but have only been back over the curve/hill once since then. Hopefully the problem is solved.

Added 9-19-05 I have gone back over the same spot 3-4 more time s and no more noises.

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gss036 · October 31, 2005

Do you have the G80 RPO code? Most 99 Z-71's don't have the limitied slip rear end. Mine doesn't although I wish it did.

Could you describe the 'errrrr' noise. When I make the noise out loud it sounds like squeeling tires.

<{POST_SNAPBACK}>

The noise sounds more like the rear disc brakes grabbing with a pieces of rock chip or something stuck between the pad and the rotor. I can look at the rotors and they are not gouged , but not a smooth wear like you would expect. It doesn't happen often enough to really listen and comes as a surprise and then it's gone again. That is what makes it tough to figure out.

Yes, I do have the G80. I have the line sheet from the Ft Wayne assy plant and it is listed under the options list. I wish I kenw what all the numbers meant, but probable just factiry codes for assebly line parts installed.

<{POST_SNAPBACK}>

Well, it has been a week since I put the rear additive in and spun the wheels real good on a gravel road and showed good lock up and I haven't had any more strange noises, but have only been back over the curve/hill once since then. Hopefully the problem is solved.

Added 9-19-05 I have gone back over the same spot 3-4 more time s and no more noises.

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Well I got the noise back on Friday. I was coming around a corner, making a left turn and it sounded like metal scrapping against metal. I went about 3 blocks, no noise, stopped and started to go again and it was there again, backed up and talked w/granddaughter I had just dropped off, she also agreed that it sounded like metal scraping in the right rear wheel/axle. I started again and no noise, drove about 3-4 miles next day, no noise. I am wonder where to start looking? Brakes or axles? I only have 35000 miles on the rig.

Bish · October 31, 2005

Do you have the G80 RPO code? Most 99 Z-71's don't have the limitied slip rear end. Mine doesn't although I wish it did.

Could you describe the 'errrrr' noise. When I make the noise out loud it sounds like squeeling tires.

<{POST_SNAPBACK}>

The noise sounds more like the rear disc brakes grabbing with a pieces of rock chip or something stuck between the pad and the rotor. I can look at the rotors and they are not gouged , but not a smooth wear like you would expect. It doesn't happen often enough to really listen and comes as a surprise and then it's gone again. That is what makes it tough to figure out.

Yes, I do have the G80. I have the line sheet from the Ft Wayne assy plant and it is listed under the options list. I wish I kenw what all the numbers meant, but probable just factiry codes for assebly line parts installed.

<{POST_SNAPBACK}>

Well, it has been a week since I put the rear additive in and spun the wheels real good on a gravel road and showed good lock up and I haven't had any more strange noises, but have only been back over the curve/hill once since then. Hopefully the problem is solved.

Added 9-19-05 I have gone back over the same spot 3-4 more time s and no more noises.

<{POST_SNAPBACK}>

Well I got the noise back on Friday. I was coming around a corner, making a left turn and it sounded like metal scrapping against metal. I went about 3 blocks, no noise, stopped and started to go again and it was there again, backed up and talked w/granddaughter I had just dropped off, she also agreed that it sounded like metal scraping in the right rear wheel/axle. I started again and no noise, drove about 3-4 miles next day, no noise. I am wonder where to start looking? Brakes or axles? I only have 35000 miles on the rig.

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Look at the backing plates on the rear discs. When mine started to heavily rust, they expanded to contact the rotor. It started only on left turns then gradually got worse. If it is the backing plate, I bent it away from the rotor and it worked for a while but eventually got bad enough to replace. Unfortunately, the backing plates require pulling each axle to replace. All in all took 45 minutes the first side and about 15 on the second.

sjspor · November 1, 2005

Pull the wheels and check the brakes, i bet the pads are still good, but the cut in the rotor is so deep that that backing of the pads is hitting the ridge on outside of the rotor.

gss036 · November 1, 2005

SJSPOR, not sure I follow you, what would cause the cut in the rotor, I only have about 35,000 miles on the rig. Hopefully I will have time tomorrow to take a look.

Bish · November 2, 2005

SJSPOR, not sure I follow you, what would cause the cut in the rotor, I only have about 35,000 miles on the rig. Hopefully I will have time tomorrow to take a look.

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As the pads/rotor wear, they wear material away from the rotor. As this happens, you will see a thin ring around the very outside of the braking surface of the rotor where the pad does not wear down the rotor. If this "ridge" is tall enough, it will contact the metal backing plate of the disc pad. Also check the backing plates while you are inspecting.

1999Silverado · November 3, 2005

Do you have the G80 RPO code? Most 99 Z-71's don't have the limitied slip rear end. Mine doesn't although I wish it did.

Could you describe the 'errrrr' noise. When I make the noise out loud it sounds like squeeling tires.

<{POST_SNAPBACK}>

The noise sounds more like the rear disc brakes grabbing with a pieces of rock chip or something stuck between the pad and the rotor. I can look at the rotors and they are not gouged , but not a smooth wear like you would expect. It doesn't happen often enough to really listen and comes as a surprise and then it's gone again. That is what makes it tough to figure out.

Yes, I do have the G80. I have the line sheet from the Ft Wayne assy plant and it is listed under the options list. I wish I kenw what all the numbers meant, but probable just factiry codes for assebly line parts installed.

<{POST_SNAPBACK}>

Well, it has been a week since I put the rear additive in and spun the wheels real good on a gravel road and showed good lock up and I haven't had any more strange noises, but have only been back over the curve/hill once since then. Hopefully the problem is solved.

Added 9-19-05 I have gone back over the same spot 3-4 more time s and no more noises.

<{POST_SNAPBACK}>

Well I got the noise back on Friday. I was coming around a corner, making a left turn and it sounded like metal scrapping against metal. I went about 3 blocks, no noise, stopped and started to go again and it was there again, backed up and talked w/granddaughter I had just dropped off, she also agreed that it sounded like metal scraping in the right rear wheel/axle. I started again and no noise, drove about 3-4 miles next day, no noise. I am wonder where to start looking? Brakes or axles? I only have 35000 miles on the rig.

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I had this exact same sound / problem with my truck. I thought that it was the rear brakes for the longest time... it seemed that it would only happen if I backed up. Then later on (couple of weeks) while driving down the road, it sounded like I was dragging something. Then the truck would "ping" when I put it in reverse. Had the wife come out and put the truck in drive and then reverse while I crawled underneath to try to locate the problem.

Short story - check your u-joints. All of mine were tight... I had made sure of that. But what I didnt see was that one of the journal slingers (plastic cap on the u-joints that holds the grease & needle bearings in) had come off and allowed all of my grease to seep out. Basically turned my needle bearings into dust. Literately. Replace both front and rear (both on rear axle) u-joints in a matter of a few hours. Problem and noise completely gone.

Something for you to look at. The sound and problem you describe sound almost exactly what I heard on mine.

Silverado

gss036 · November 3, 2005

I quickly looked last night and the caps appeared to be on the "U" joints and they are tight, but like you said, can't see inside. I also checked the rear brake disc, I don't feel a ridge on them. I tried to remove the tire but could not get the nuts off as Les Schwabs really torqued them down. I had a torque wrench that read 140 #s and they did not budge. Mystery goes on.