2004 GMC Sierra Rear end noise

2004 GMC SIERRA
108,000 MILES
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ROLAND0305
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Last week I bought a 2004 GMC Sierra 1500 from a private seller, seemed like a legit guy. Well he said that he had just had the whole rear end rebuilt, come to find out it was just the bearings and right axle. After driving it a few days whenever it would get warmed up there would be a terrible popping/ clunking coming from the rear differential. I spoke to the mechanic who rebuilt it and he said I would need to replace the clutch packs. Then when I was calling a few parts stores I had a guy tell me I might want to try changing the oil and adding the friction modifier since it was a limited slip and the mechanic probably didn't add it. This fixed the problem, but the past couple days I have noticed after driving it there will be a slight grinding coming from the back end when i turn the pick up off. Is this a big problem or something i don't need to worry about?
Oct 3, 2013 at 12:33 PM
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SATURNTECH9
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so you hear agrinding with the truck not moving and your in park and your turning the engine.off?
Oct 3, 2013 at 12:52 PM
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ROLAND0305
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Yes, like a grinding/ humming. Like something is rotating with bad bearings
Oct 3, 2013 at 12:56 PM
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SATURNTECH9
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if you don't.start it and just turn.the key to the run.position can you hear it?
Oct 3, 2013 at 1:03 PM
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ROLAND0305
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No, no i can't
Oct 3, 2013 at 1:05 PM
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SATURNTECH9
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if the truck isn't moving where is the noise coming from rear pumpkin?also you can't hear it while moving?
Oct 3, 2013 at 1:13 PM
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ROLAND0305
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As far as i can tell the rear pumpkin. And no, at least not over the exhaust
Oct 3, 2013 at 1:15 PM
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SATURNTECH9
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how about when coming to.stop?sometimes those clutches stick don't.always fully release when.coming to.a stop
Oct 3, 2013 at 1:37 PM
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ROLAND0305
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I will have to check and see. But if this is the case would anything need to be done?
Oct 3, 2013 at 1:39 PM
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SATURNTECH9
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also while making turn's see if you can.hear it what kind.of friction.modifier did you use ?
Oct 3, 2013 at 1:51 PM
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ROLAND0305
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It sounds fine. I don't recall what kind it was, i got it at carquest
Oct 3, 2013 at 2:35 PM
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SATURNTECH9
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I personally use the Ford motorcraft friction modifier it works reallywell.
Oct 3, 2013 at 3:05 PM
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ROLAND0305
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Well what i got fixed my original problem. I guess i will just see what happens now, as long as it doesnt tear anything else up i can live with the noise
Oct 4, 2013 at 8:21 AM
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SATURNTECH9
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it's really strange how it.happens.when.the truck isn't.moving and your.turning the key off?
Oct 4, 2013 at 11:53 AM