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Discussion Starter · #1 ·
Hi everyone,
I have a light erratic drumming sound from possibly the right rear. It is random at all speeds but gets a little louder above 40mph. It's not in sync with the speed. Rear brakes, calipers and rotors replaced about 3k ago. I checked torque on leaf spring u bolts, lug nuts and removed lower bolt on the shock to check it, its ok too. Nothing loose or rubbing on exhaust or drive shaft. Differential oil replaced about 3k ago, no metal in it, put in exact manufacturer oil and filled exactly.

Any help is appreciated!
 

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2003 Silverado 1500 LS
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Jack up and rotate wheels by hand. If you hear the noise, try to track it down.

Try to move them in all directions to check for any excess play. If you feel excess play, note the direction of the movement, that will give you the clue.

Check u-joints carefully, and check all fluid levels in the diffs and transfer case.

Could also be tire noise..........................
 

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Discussion Starter · #3 ·
Jack up and rotate wheels by hand. If you hear the noise, try to track it down.

Try to move them in all directions to check for any excess play. If you feel excess play, note the direction of the movement, that will give you the clue.

Check u-joints carefully, and check all fluid levels in the diffs and transfer case.

Could also be tire noise..........................
Thanks!
If there is play in a certain direction what clue is that?
I know how to check for bad wheel bearings but not sure on the diff.
 

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Mostly bad wheel bearings. Don't forget, you've got wheel bearings in rear too, excess up/down movement in wheel would be indicator. There basically should be no discernible movement in any on the wheels. Though you might have a tick of in/out movement in the rears, that's normal.
 

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Discussion Starter · #5 · (Edited)
Top to bottom play is slight, enough to say bearing is bad. But pulling the wheel in/out is a good 1/16. Feels real bad, left rear is half as bad as the right going in/out. These are both on rear. Edit: I read 1/16 is ok. But top to bottom has slight movement and along with the noise symptom I guess bearing.
Thanks for staying with me on this.
 

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Yeah, the in/out at 1/16" is no big deal. Someone here had the spec on that up/down and I think it was .010", which is not much.

One thing you might do, is jack up the rear, and support it SAFELY. Then start truck, in 2WD mode, put foot on brake, then put in D and rev the engine gently to see if you hear the noise. Maybe just let it idle with wheels spinning and you go back and listen. Gotta be extra careful doing something like this, but I've done it numerous times to check for issues.

If you have a dial caliper, you could easily get a true measure of the up/down. Just use the edge of a wheel or maybe even a tire would work, there's not much tension of end of the caliper.

But I'm not sold on a bad bearing yet. Too many other possibilities................
 

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You are describing two differing styles of caliper. I'm not a great typist, so here is some info from HAYNES below. My comments are in green.


"There are several types of calipers:

Floating calipers
A floating brake caliper contains a piston on only one side, but has pads that make contact with both sides of the brake disc. The caliper slides back and forth on bushings or pins. When the brakes are applied, the piston pushes the brake pad on the inboard side of the disc. The caliper then slides on the bushings or pins, which squeezes the outboard pad against the rotor, initiating braking action.
This is absolutely the most common type of caliper, with many having two pistons instead of just one. This type of caliper is used on our trucks in front and rear.

Sliding brake calipers
A sliding brake caliper works in much the same way as a floating caliper, but is mounted in a slot in the caliper adapter. When you hit the brakes, it uses its single piston press the inner pad against the rotor, then the movable frame of the caliper applies pressure to the other brake pad, pressing it against the disc.
Rarely used

Fixed brake calipers
A fixed caliper is mounted to a bracket, and as the name suggests it doesn't move. It usually contains two, four, six or even eight pistons. The fixed caliper consists of an equal number of pistons on both the inboard and outboard halves of the caliper. It is generally accepted that these have better performance, but cost more. That's why fixed calipers with multiple pistons tend to be installed on high-performance cars."
Sports cars and high-end tend to use this type of caliper
 

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Discussion Starter · #9 ·
You are describing two differing styles of caliper. I'm not a great typist, so here is some info from HAYNES below. My comments are in green.


"There are several types of calipers:

Floating calipers
A floating brake caliper contains a piston on only one side, but has pads that make contact with both sides of the brake disc. The caliper slides back and forth on bushings or pins. When the brakes are applied, the piston pushes the brake pad on the inboard side of the disc. The caliper then slides on the bushings or pins, which squeezes the outboard pad against the rotor, initiating braking action.
This is absolutely the most common type of caliper, with many having two pistons instead of just one. This type of caliper is used on our trucks in front and rear.

Sliding brake calipers
A sliding brake caliper works in much the same way as a floating caliper, but is mounted in a slot in the caliper adapter. When you hit the brakes, it uses its single piston press the inner pad against the rotor, then the movable frame of the caliper applies pressure to the other brake pad, pressing it against the disc.
Rarely used

Fixed brake calipers
A fixed caliper is mounted to a bracket, and as the name suggests it doesn't move. It usually contains two, four, six or even eight pistons. The fixed caliper consists of an equal number of pistons on both the inboard and outboard halves of the caliper. It is generally accepted that these have better performance, but cost more. That's why fixed calipers with multiple pistons tend to be installed on high-performance cars."
Sports cars and high-end tend to use this type of caliper
long story short, bearing oil must have drained back towards the diff after many hours with both axles lifted up. It’s evident now from the sound that the left rear bearing is real bad. Can’t be sure about the right because part of the noise transfers over. Going to have both replaced at the dealer. They don’t gouge here, maybe a hundred extra but worth it.

Thanks for help! It kept me going long enough to find it.
 

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Nice!! Good find, and good luck. ;)

I will add something here that might come in handy. If the bearing(s) are badly worn, there's a good chance the axle might be worn down in that contact area. Thus you'd need a new axle, which would be expensive at the dealer... BUT ...... there are some bearings available that are offset, so that the roller bearings contact a virgin part of the axle, and this way you can confidently use the old axle. If the dealer calls and says "you need two new axles", try and suggest the offset bearings to them.

Please post results when done. 🇺🇲
 

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Discussion Starter · #11 ·
Nice!! Good find, and good luck. ;)

I will add something here that might come in handy. If the bearing(s) are badly worn, there's a good chance the axle might be worn down in that contact area. Thus you'd need a new axle, which would be expensive at the dealer... BUT ...... there are some bearings available that are offset, so that the roller bearings contact a virgin part of the axle, and this way you can confidently use the old axle. If the dealer calls and says "you need two new axles", try and suggest the offset bearings to them.

Please post results when done. 🇺🇲
When I google offset bearings all I’ve found so far is stuff for offset wheels. Have a link?
 

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It's been 20 years since I used them. I just looked, and I can't find them any more. Perhaps discontinued.....

I tried to find a new axle for 2003 GMC 1500 on a GM parts supplier site that I use all the time, but it says 'discontinued', so if your dealer has to install a new axle, it would likely be aftermarket. I looked one up and it wasn't expensive, saw them for $125 to $175 each, not too bad at all. So don't worry about it.
 
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