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  1. #1

    Default Squealing sound at 1600-1800rpm only?

    I've got a 99 GMC Sierra classic, 4x4 with only 50k on it, had it for about a month now. Picked up a weird squealing sound under light throttle only and only around 1600-2000rpm and also only at normal operating temperature. Let off the gas and it stops, mash the gas and it stops. It can happen at any speed but makes no sound when I kick it into neutral and let it coast. However I can't reproduce the sound sitting in the driveway in neutral or power braking it.

    Front wheel bearings feel tight, no leaks around any CV-joint boots, just replaced the belt, tensioner and pulley and idler pulley. Just replaced the u-joints in the rear driveline. All the brakes are nearly brand new and I just cleaned all the dust out. Also drained and refilled the diffs but the oil looked brand new - mostly likely changed at the dealership before I bought it.

    Still have the noise. I put a metal rod on the alternator to listen and heard a pretty good whirring noise coming off of it but compared it to my 97 Expedition alternator and it is basically an identical noise so I'm doubting that is the problem. Neither the water pump or A/C compressor sounded bad either.

    I don't want to keep sinking $$ into it guessing what's wrong but this noise is driving me crazy!

    The gremlin under the hood is having too much fun...

    Any suggestions as to what I might check next?
    -Berg
    1998 GMC Sierra 1500 Ext Cab 4x4

  2. #2
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    Default

    I was gonna suggest belt tensioner, but if it doesnt do it when parked then I am not too sure. Power steering fluid low??
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual
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  3. #3

    Default noise

    Sounds like it may be in the tranny. You say it is gone when you coast--makes me think that may be it???

  4. #4

    Default

    I was wondering about the tranny but it doesn't seem to matter what gear I'm in and like I said before it could be at 20mph or 50mph. For example, it will be squealing in that RPM range when I'm in drive, it shifts into OD and stops because the RPMs drop. Get up to speed in OD and the squeal comes back again intermittently. Step on it, it shifts down into drive changing the RPM, and the squeak disappears.

    What would/could it be in the tranny - an output bearing on the transfer case maybe?

    All fluid levels are full and I've greased every point that I can find front to back.

  5. #5

    Default

    On some cars that have aftermarket intake kits on them they make a squealing noise. And they actually do it more when the intake tube comes off. maybe you have a break in your intake tube. maybe it came off the throttle body.

    2008 Chevy Silverado WT for sale
    All black with DJM 4/7 drop sold
    Factory Navi for sale
    22inch Escalade wheels sold

  6. #6

    Default

    It could also be a idler pulley or tensioner. The bearings go bad and they will make noise.

  7. #7

    Default

    All new pulleys and tensioner and belt 2008blackWT...

    I have an Air Raid TBI spacer and a K&N cold air intake kit on it. I just learned that the tiny whistle under heavy throttle means that the AirRaid spacer is doing it's thing and it's not a vacuum leak that is making that sound.

    I would expect with a more major crack or break in the intake resulting in a vacuum leak I would be experiencing other problems like a rough/poor idle which I'm not. This sound is more like a metal on metal squeal, only at operating temperature, only in gears 2, Drive or OD, (couldn't make it squeal in Low), both in 4wd and 2wd, and now is randomly present around 1400-2200 RPM, a little wider range than before.

    Still cannot reproduce the sound in the driveway - I'm hoping a buddy's son can put it on a lift at the shop he works at after hours and see if we can narrow it down but that's hit and miss since he's fairly new there.

    I hate to just drive it 'til it breaks but that's almost where I'm at...
    Last edited by berg; 07-29-2009 at 01:15 PM.

  8. #8

    Default

    2008blackWT - I believe you are the winner.

    I had the truck up on blocks for a half hour and could not reproduce the squeal - I was starting to think it may be the clutch fan but it showed no signs of wear.

    My truck has an AirRaid TBI Spacer that doesn't really work well with the K&N intake because the K&N won't sit flush. I bought a longer piece of 4" silicone hose, cut it at an angle to accommodate the K&N sitting slightly off, added a little silicone sealer as I clamped it all together. Double checked all my other connections and clamps as well.

    I've put about 400 miles on it now without a peep! I still can't believe that a leak on the aftermarket air intake connection could create that kind of a metal on metal squeal. It really sounded like a bearing going out to me.

    Anyway, thanks for the help and advice!

  9. #9

    Default

    Quote Originally Posted by berg View Post
    2008blackWT - I believe you are the winner.

    I had the truck up on blocks for a half hour and could not reproduce the squeal - I was starting to think it may be the clutch fan but it showed no signs of wear.

    My truck has an AirRaid TBI Spacer that doesn't really work well with the K&N intake because the K&N won't sit flush. I bought a longer piece of 4" silicone hose, cut it at an angle to accommodate the K&N sitting slightly off, added a little silicone sealer as I clamped it all together. Double checked all my other connections and clamps as well.

    I've put about 400 miles on it now without a peep! I still can't believe that a leak on the aftermarket air intake connection could create that kind of a metal on metal squeal. It really sounded like a bearing going out to me.

    Anyway, thanks for the help and advice!
    this is y i love this site... can get help from many views and ppl and fix ur problems

  10. #10

    Default

    Do you have the ac on when the squealing happens My 03 gmc does it to about 2000 rpm but it only happens when the ac is on I think it might be the ac compressor

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