Site Sponsors & Vendors
Page 1 of 2 12 LastLast
Results 1 to 10 of 19

Thread: Need help diagnosing a fluttering noise on acceleration

  1. #1
    Senior Member bjhayes's Avatar
    Join Date
    Jul 2009
    Location
    Richmond, TX
    Posts
    280
    Post Thanks / Like

    Default Need help diagnosing a fluttering noise on acceleration

    I've started hearing a 'fluttering' sound on acceleration but only when my engine is cold. After 10 or so minutes of driving the sound is not there anymore. Dealer kept the car overnight but of course everything is normal sounds to them so it's up to me to narrow down the culprit and I need some suggestions.

    The best way I can describe it is a muffled sound of a card in a bike spoke (very different from a tick). Noticeable in the cabin if the radio is turned down. Very noticeable as I drive by walls, other cars and it bounces off.

    I first noticed it within a week or so after dealer replaced my leaking oil pan gasket. Maybe coincidence but also wondering if the oil pan removal procedure has anything where they unbolt any part of the exhaust? Possible exhaust leak?

    Oil life and levels are good.
    Car is a 2009.1 w/ 64k miles, is my daily driver, and is all stock except for the Rotofab intake.
    I do not notice any difference in how it drives.. seems to have same power, response, etc...

    Any ideas?

    I am the original owner and still have till Feb 2015 on my GMPP extended warranty so any input I can get to narrow this down to something that should be covered and I can get the dealer to recognize is much appreciated. Even if it turns out to be something not covered I'm fine with that too just need to get this taken care of.
    Last edited by bjhayes; 04-17-2014 at 04:36 AM. Reason: clarifications
    '09 LR G8GT w/ Premium / Sport / Sunroof / 35% Tint
    Conti-DW Extremes

  2. #2
    Administrator Chewy's Avatar
    Join Date
    Aug 2008
    Location
    Bettendorf, IA
    Posts
    7,298
    Post Thanks / Like

    Default

    Probably piston slap. It's common with the L76 and only happens when cold.

    2009.5 MSM GXP 500ish N/A RWHP. Mods include but aren't limited to: Texas Speed 418 (6.8L) fully forged held together with ARP from top to bottom, PRC 255cc heads, Rick Crawford intake plenum, TB port, polish and tune, Roto-Fab 102mm CAI w/LS7 MAF, Kooks 1-7/8" headers wrapped with DEI, Corsa catless system, Circle D 3200 Stall, 3.45 final drive, BMR's complete street bushing kit and sway bars, Eibach Pro Kit, G-Force Axles, running on staggered VMR 710's with Bridgestone RE11 rubber. HSV triple gauge pack with Calais smokers kit mod, V6 tails, debadge/rebadge, V6 door handles, AU black door trim, Maverick Man under hood strut covers, & washer and bolt kit, fully corrected paint thanks to Adams Polishes and my hard work. Built with reliability in mind with some power for those times when you need to pass or go over a big hill. Just a poser, not a racer!

  3. #3
    Senior Member bjhayes's Avatar
    Join Date
    Jul 2009
    Location
    Richmond, TX
    Posts
    280
    Post Thanks / Like

    Default

    Quote Originally Posted by Chewy View Post
    Probably piston slap. It's common with the L76 and only happens when cold.
    hmmm.. Could be.. but I've never noticed it before and I quickly notice any difference in sound or feel with my car. If it is piston slap why would it all of a sudden start doing this after 5 years.
    '09 LR G8GT w/ Premium / Sport / Sunroof / 35% Tint
    Conti-DW Extremes

  4. #4
    Administrator Chewy's Avatar
    Join Date
    Aug 2008
    Location
    Bettendorf, IA
    Posts
    7,298
    Post Thanks / Like

    Default

    Time doesn't have as much to do with it as use. My GT did it, but it went away pretty quickly. I'm not saying that's it, but it sounds like what you're experiencing. It could be that it's just getting worse and more noticeable.

    Chris

    2009.5 MSM GXP 500ish N/A RWHP. Mods include but aren't limited to: Texas Speed 418 (6.8L) fully forged held together with ARP from top to bottom, PRC 255cc heads, Rick Crawford intake plenum, TB port, polish and tune, Roto-Fab 102mm CAI w/LS7 MAF, Kooks 1-7/8" headers wrapped with DEI, Corsa catless system, Circle D 3200 Stall, 3.45 final drive, BMR's complete street bushing kit and sway bars, Eibach Pro Kit, G-Force Axles, running on staggered VMR 710's with Bridgestone RE11 rubber. HSV triple gauge pack with Calais smokers kit mod, V6 tails, debadge/rebadge, V6 door handles, AU black door trim, Maverick Man under hood strut covers, & washer and bolt kit, fully corrected paint thanks to Adams Polishes and my hard work. Built with reliability in mind with some power for those times when you need to pass or go over a big hill. Just a poser, not a racer!

  5. #5
    Super Stock! I12XLR8's Avatar
    Join Date
    Jan 2011
    Location
    ON, CAN
    Posts
    2,305
    Post Thanks / Like

    Default

    Is piston slap ever covered under warranty? I'm bringing mine in for what I think is a slap problem as well


    Sent from my iPhone using Tapatalk
    R.I.P. Charlie. We are all here because of you

    "I have dreamed a dream, and now that dream has gone from me" - Morpheus of the Nebuchadnezzar, and Grant of I12XLR8.



    'Luskville is a cool experience, Calabogie is incredible, Mosport is life altering'


  6. #6
    Senior Member bjhayes's Avatar
    Join Date
    Jul 2009
    Location
    Richmond, TX
    Posts
    280
    Post Thanks / Like

    Default

    Ok... This morning I only noticed it when in gear. In neutral or park I can not hear it... But put it in drive and start accelerating I can. I found a post on a a GMC truck board that describes exactly what I'm experiencing but no one there has responded yet and I'm going to watch that thread too. (http://www.silveradosierra.com/uncat...n-t222722.html).

    This all started after the oil pan gasket was replaced. I'm wondering what is involved in that procedure to possibly cause this. Exhaust leak? Motor mount?
    '09 LR G8GT w/ Premium / Sport / Sunroof / 35% Tint
    Conti-DW Extremes

  7. #7
    Senior Member bjhayes's Avatar
    Join Date
    Jul 2009
    Location
    Richmond, TX
    Posts
    280
    Post Thanks / Like

    Default

    Ok... This morning I only noticed it when in gear. In neutral or park I can not hear it... But put it in drive and start accelerating I can. I found a post on a a GMC truck board that describes exactly what I'm experiencing but no one there has responded yet and I'm going to watch that thread too. (http://www.silveradosierra.com/uncat...n-t222722.html).

    This all started after the oil pan gasket was replaced. I'm wondering what is involved in that procedure to possibly cause this. Exhaust leak? Motor mount?
    '09 LR G8GT w/ Premium / Sport / Sunroof / 35% Tint
    Conti-DW Extremes

  8. #8
    VIP Member G8 GT V8's Avatar
    Join Date
    Jun 2009
    Location
    Fairfield, Ohio
    Posts
    1,967
    Post Thanks / Like

    Default

    I wonder if it is something loose in your exhaust and while the engine is under load, in gear, it's torque twisting just enough to have an issue. It would be worth asking the shop if they loosened your exhaust when changing the gasket. Or, if you're mechanically inclined, you could crawl under to see if you find anything loose.
    Marty

    G8 gone, but not forgotten...

  9. #9
    Senior Member bjhayes's Avatar
    Join Date
    Jul 2009
    Location
    Richmond, TX
    Posts
    280
    Post Thanks / Like

    Default

    Quote Originally Posted by G8 GT V8 View Post
    I wonder if it is something loose in your exhaust and while the engine is under load, in gear, it's torque twisting just enough to have an issue. It would be worth asking the shop if they loosened your exhaust when changing the gasket. Or, if you're mechanically inclined, you could crawl under to see if you find anything loose.
    Shop was GM dealership that replaced the gasket under warranty. They have done work on the car since new and I have not had any real problems with them. When I ask them about the noise afterwards they say they don't hear anything that is not normal.

    Does the GM gasket replacement procedure require any unbolting of exhaust?

    Being mechanically inclined is not a problem... My biggest problem is having the time to get to it and the limited space I have to work on it.

    Went out again today at lunch (cold start with air temp in the low 70s) and was able to confirm I only hear it in gear while accelerating. As I started to hear it I shifted up to neutral and gave some light throttle and sound is not there anymore (or so slight I can't hear it)... then I shifted back to drive and gave some light throttle and there it is again. After 10 or so minutes of driving it's no longer notiecable at all.

    It may be piston slap but seems odd it would only be noticeable when in gear under load. Makes me think something in the exhaust leak side... but who knows.
    '09 LR G8GT w/ Premium / Sport / Sunroof / 35% Tint
    Conti-DW Extremes

  10. #10
    Administrator Chewy's Avatar
    Join Date
    Aug 2008
    Location
    Bettendorf, IA
    Posts
    7,298
    Post Thanks / Like

    Default

    I only heard the piston slap on my GT when under a load. I always made sure to take it easy until up to running temp.

    2009.5 MSM GXP 500ish N/A RWHP. Mods include but aren't limited to: Texas Speed 418 (6.8L) fully forged held together with ARP from top to bottom, PRC 255cc heads, Rick Crawford intake plenum, TB port, polish and tune, Roto-Fab 102mm CAI w/LS7 MAF, Kooks 1-7/8" headers wrapped with DEI, Corsa catless system, Circle D 3200 Stall, 3.45 final drive, BMR's complete street bushing kit and sway bars, Eibach Pro Kit, G-Force Axles, running on staggered VMR 710's with Bridgestone RE11 rubber. HSV triple gauge pack with Calais smokers kit mod, V6 tails, debadge/rebadge, V6 door handles, AU black door trim, Maverick Man under hood strut covers, & washer and bolt kit, fully corrected paint thanks to Adams Polishes and my hard work. Built with reliability in mind with some power for those times when you need to pass or go over a big hill. Just a poser, not a racer!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •