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  1. #1
    Sr. Apprentice msvx95's Avatar
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    Mentor, Ohio
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    Default Can't diagnose a noise from the backend

    I've taken my truck to a tech in the past and they couldn't diagnose it, but my issue is a strange noise coming from the rear of the truck. It happens when approaching a stop and going over some minor bumps...sounds like a low tone (boop, boop)...I had all 4 shocks replaced last year and I've pushed the truck up and down on the bumper and no noise. It happens at low speeds and when the brake is applied also low speeds without the brakes applied. I can't pinpoint what would be making the noise...rear hubs, u-joint, etc.
    Anyone have this kind of problem before or know what it could be?
    Matt


  2. #2
    Jr. Mechanic
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    Apr 2010
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    Ortonville MI
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    Default

    Do you have receiver in your hitch? Mine will make a noise like that once in a while.

    07 NBS Crew cab SLT 4x4

  3. #3
    Sr. Apprentice msvx95's Avatar
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    Default

    i have a hitch but no receiver. I should actually check if it's loose though, never thought of that

  4. #4
    Master Mechanic Silverado Junkie's Avatar
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    Feb 2010
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    Lead Hill, Arkansas
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    Default

    Id check and make sure everything is nice and tight.
    1995 Silverado,Z71, 3-inch lift,2-inch leveling kit, SkyJacker Suspension, short ram-air intake, throttle body spacer, MSD ignition coil, straight pipes

  5. #5
    Sr. Apprentice raf1231's Avatar
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    Default

    Just a thought, have you checked out the rear sway bar to be sure the bushing are solid along with the connecting rods? Also, make sure your exhaust pipes and muffler are not hanging to close to a frame cross member. I just replaced the muffler & tailpipe on my '92 Suburban. About the time I was going to call it done, I happened to notice the catalytic convector was a fraction of an inch above the torsion bar cross member. Is your spare tire under the bed? If so, is it bolt up tight? And nothing inside the wheel where it comes up against the bottom of the bed?

    You said you've pushed the rear end up and down, but have you tried pushing forwards and backwards?

    That's the only crazy guesses I've got. I doubt if they're of much help. I hope you figure out your problem.

    92 Suburban K1500 5.7l in transition.
    Done:
    2" lift;
    AR FUEL Blk wheels 16x8 6-spokes blk machined/add red hi-lites;
    BFG All-Terrain KO LT295/R7516/D;
    To Go:
    Blk fender flares;
    Blk frt bumper w/fog lites/grill cut-outs;
    Blk grill frame;
    Custom grill;
    Updated headlites;
    LED corner/parking/turn-signals;
    Blk rear step bumper;
    LED tail/brake/back-up;
    60" LED strip 'tween bumper/cargo drs;
    2-tone paint/orig Red prim color/dr pillars blk;
    Existing running boards will be blk.
    :sign0011: Randy

  6. #6

    Default

    had a very similar problem wen going over speedbumps or really anything jarring at slow speeds. turned out it was my muffler. the weld broke at very back, but the way it was sitting u could barely tell it had snapped so it was a mystery noise until a friend driving behind me noticed one of my mufflers bouncing more than the other. very quick fix. hope you find it!
    2009 Silverado Crew Cab LT
    20 inch Incubus Wheel
    35 Pro Comp Xtreme A/T
    Zone Offroad 6.5 suspension lift
    Dual Flowmaster Super 40s (Turn Downs)
    Low profile tool box
    Diablo Predator Programmer

  7. #7
    Sr. Apprentice msvx95's Avatar
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    Default

    Well I just checked what I can...didn't lower the spare tire, but the tire is secure, the trailer hitch is secure...leaf springs, shocks...I shook everything left and right, up and down. Not forward and back though. The muffler pipes are secure, but they appear close to the frame though by .250". I do have to force them over to touch the frame I might add.

    Sway bars? I'm not sure if they are lose...I know what they look like on my car, but are they beefier and in a different location on the truck? I didn't check those.

    I almost want to say this is a rotational noise which I hope it isn't.

  8. #8
    Sr. Apprentice raf1231's Avatar
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    Default Sway (Stabilizer( Bar)

    Wow. Describe a sway bar? I guess first I need to use contemporary language - stabilizer bar.

    You didn't say what kind of truck you have. So, I'll try describing the rear stabilizer bar on my '92 Suburban K1500. First, there are 2 brackets w/rubber bushings, welded to the bottom of the axle housing - one on each side of the differential. The stabilizer bar runs thru the brackets and then bends behind the differential housing. After passing thru the brackets, the bar bends forward and then upward. The ends of the stabilizer bar terminate with a link bar connecting the stabilizer bar to the frame. Both ends of the "link" bar have rubber bushings. If any of the bushings are worn, the stabilizer bar and the links can be rattling.

    Since you said the noise sounds rotational, I doubt the stabilizer bar has anything to do with it. But just for my own personal ego, I hope my description of the stabilizer helps you locate the stabilizer bar. (A drawing would have been so much better.)

    I'm fresh out of ideas other than try to just ignore the noise and hope it's nothing serious.

  9. #9
    Sr. Apprentice raf1231's Avatar
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    Default Can't diagnose a noise from the backend

    I've had few more thoughst - have you checked the grease level in the differential? Also, have you drained any grease from the diffy to check for metallic chips & flakes? I assume you've checked the grease seals, wheel bearings and brake parts inside the drums.

    My very last thought is have a friend follow you (maybe around a large empty parking lot) - directly behind you (up close and from a distance), then along side each quarter panel. When doing the left quarter, a second friend would be a big help since the driver would be too far away. Use some form of communications when doing this - hand signals, walkie-talkies or cell phones.

    OK, I think I'm done babbling.

  10. #10
    Sr. Mechanic trapperdon's Avatar
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    Default

    you also might want to push up and forward on your gas tank, check to see if the mounting
    brackets / straps are rubbing or slightly loose.
    could be when you brake or hit a bump it makes it rub or jiggle enough to resonate thru tank...
    :fighting0037:
    when in doubt, doubletap !

    - buying a new truck, one part at a time :grrrrrr:
    94 Blazer 4x4 k1500 5.7 L - aftermarket cold air intake
    Energy Suspension swaybar & upper and lower control arm bushings
    Pro Comp ES 9000 front shocks, new front drive axles,
    stainless front brake rotors & new pads,
    new Moog front end ball joints, Smittybilt black nerf bar steps,
    MB Racing rims & Hankook ATm off road tires

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