Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Flowmaster shake rattle and roll poll

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by smack, Mar 12, 2002.

  1. smack

    smack 1/2 ton status

    Joined:
    Feb 24, 2000
    Posts:
    277
    Likes Received:
    0
    Location:
    Colorado
    This weekend I replaced my rusted out dual exhaust with series 40 flowmasters. Simply revving the engine in the driveway causes some very noticable vibrations -- which I did have to a lesser degree with my rusted out old mufflers. The vibrations are most noticable when I hold the rpms at around 2000. My question is, could I have an engine problem (harmonic balancer, damaged flywheel, mounts) or is this just the nature of the flowmaster beast? BTW, the engine is brand new, installed by chevy 8 thousand miles ago. Would a damaged flywheel act like this?
    Thanks in advance,
    Jason
     
  2. JK5

    JK5 1/2 ton status GMOTM Winner

    Joined:
    Jan 31, 2002
    Posts:
    3,453
    Likes Received:
    1
    Location:
    Norton, Oh
    I have Flowmasters on my truck, no vibs here, the only problem I had was noise!
     
  3. smack

    smack 1/2 ton status

    Joined:
    Feb 24, 2000
    Posts:
    277
    Likes Received:
    0
    Location:
    Colorado
    Doesn't the noise itself cause vibrations???
     
  4. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

    Joined:
    Jul 18, 2001
    Posts:
    5,693
    Likes Received:
    0
    Location:
    CA
    I experience this in my car warming it up in the driveway at 2500 rpms only for some reason.
    It is internally balanced, and i'm almost positive its just the resonance from those loud speaker flowmasters./forums/images/icons/smile.gif
    When you got a sore back from wrenching, and you want a massage... it's the only way to go./forums/images/icons/cool.gif
     
  5. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Joined:
    Nov 28, 2000
    Posts:
    3,112
    Likes Received:
    1
    Location:
    Western Massachusetts
    I believe it's known as resonation (sp??). They say you will hear some, and the amount will vary by muffler location (further forward vs. furthur back), tubing diameter, cats or no cats, h-pipe or no h-pipe, harmonics of your interior, etc. It could be a vibration elsewhere (tranny or motor) combined with the resonation, so who knows. You may see if you can find a cheap pair of stockers to throw on there to see if it makes a difference in vibration (hopefully you didn't have them welded in, which makes swapping mufflers a problem).
     
  6. smack

    smack 1/2 ton status

    Joined:
    Feb 24, 2000
    Posts:
    277
    Likes Received:
    0
    Location:
    Colorado
    Resonation maybe, but how do I tell if I have a bad flywheel or balancer???
     
  7. 90K5

    90K5 1/2 ton status

    Joined:
    Jun 1, 2000
    Posts:
    3,719
    Likes Received:
    0
    Location:
    Lubbock, TX
    check all the exhaust hangers. Mine were really loose and made a lot of noise. Sometimes the rear leafs on our K5's break the hangers
     
  8. smack

    smack 1/2 ton status

    Joined:
    Feb 24, 2000
    Posts:
    277
    Likes Received:
    0
    Location:
    Colorado
    All the hangers are tight, but thanks
     
  9. CaptCrunch

    CaptCrunch 1/2 ton status

    Joined:
    Feb 2, 2001
    Posts:
    3,596
    Likes Received:
    1
    Location:
    Minnesota
    do you have solid hangers or ones with the rubber bushing? Solid mounts will do it
     
  10. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Joined:
    Nov 28, 2000
    Posts:
    3,112
    Likes Received:
    1
    Location:
    Western Massachusetts
    That I don't know (on the vehicle). You would have to take them off and bring them to a place that can spin balance them (not sure of the feasability of that).
     
  11. smack

    smack 1/2 ton status

    Joined:
    Feb 24, 2000
    Posts:
    277
    Likes Received:
    0
    Location:
    Colorado
    Only the last one at the bend on the left side has a sold hanger, all others are rubber bushings.
     
  12. JK5

    JK5 1/2 ton status GMOTM Winner

    Joined:
    Jan 31, 2002
    Posts:
    3,453
    Likes Received:
    1
    Location:
    Norton, Oh
    At first, I tried the flowmasters w/o tailpipes and w/o a crossover pipe, it didn`t run that well and was very loud!!! After installing tailpipes and crossover pipe, there was a huge inprovement in the way it ran and sounded, but I never had any vibration!!! Did you try calling the Flowmaster Tech line? Those guys could probably answer any questions you have!!! I called a couple of times!!! They were very helpful!!!
     
  13. smack

    smack 1/2 ton status

    Joined:
    Feb 24, 2000
    Posts:
    277
    Likes Received:
    0
    Location:
    Colorado
    Well I just got off the phone with the flowmaster tech line and they weren't very helpful except that he said the 40 series is the most aggressive in sound and that not using cats (like me) could really create a large resonance -- but he said if the whole truck is vibrating there could be something wrong with the motor.
    Again I ask, how do I know if I have a bad flywheel/dampner?
     
  14. Blazer79

    Blazer79 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,816
    Likes Received:
    0
    Location:
    Guatemala, Central America
    Could it be your engine mounts didn't get replaced? I think that if the balancer/flywheel were bad, it would be a very noticeable shake that speeds up as you rev your Blazer.

    I'd recommend you find an old, experienced mechanic who will just sit in your Blazer and tell you exactly what it is. Those old guys can smell the problems as soon as they are in the same block as your Blazer.

    I forgot: I also have two 40 series flowmasters with an H pipe, and there are no significant vibrations.
     
  15. white-rhyno

    white-rhyno 1/2 ton status

    Joined:
    Jan 27, 2002
    Posts:
    942
    Likes Received:
    0
    Location:
    Ellensburg Washington
    I believe that you just have a bad case of interior resonance. Mine gets so bad it hurts your ears and gives you a headache. Crosspipe should help
     
  16. smack

    smack 1/2 ton status

    Joined:
    Feb 24, 2000
    Posts:
    277
    Likes Received:
    0
    Location:
    Colorado
    Maybe the H pipe is the way to go -- do you guys have any suggestions/pictures of how you set yours up?? From under my truck it doesn't look like there's any room up front unless you send them down on a 45degree angle to clear the frame.
     
  17. 79Beast

    79Beast 1/2 ton status

    Joined:
    Dec 9, 2001
    Posts:
    1,155
    Likes Received:
    0
    Location:
    Georgia
    Resonance is your problem. Add a crossover pipe as close to your headers?/manifolds as possible. This will make it run quieter and change the resonance hopefully enough to put it into a different and less obnoxious frequency. Your flywheel will not go out of balance. It is unlikely for it to be damaged while on the vehicle. To check it for straightness, remove dustcover, crank the truck, hold a pencil or some sort of straight edge very close to the flywheel. There should be a consistant distance between your flywheel and straightedge maintained during the entire revolution. The harmonic balancer should also be shecked the same way. It should also be replaced if the elastomer is gone or "ate up". Make sure your engine is running smoothly. A better flowing exaust can lean out your air/fuel mixture.
     
  18. smack

    smack 1/2 ton status

    Joined:
    Feb 24, 2000
    Posts:
    277
    Likes Received:
    0
    Location:
    Colorado
    Thanks, I'll do the pencil test tonight. Any pixs or suggestions of crossover pipes??
     
  19. bigmack

    bigmack 1/2 ton status

    Joined:
    Jan 3, 2002
    Posts:
    478
    Likes Received:
    0
    Location:
    Tennessee
    Do you have tailpipes running out the back ? I had some exhaust on my truck that had turndowns just in back of the mufflers & it would vibrate the windows, I ran the pipes all the way out the back of the truck and it fixed the problem.
     
  20. 79Beast

    79Beast 1/2 ton status

    Joined:
    Dec 9, 2001
    Posts:
    1,155
    Likes Received:
    0
    Location:
    Georgia
    Here's the thing: in the pencil test you are looking for a variation. You want both balancer and flywheel to be round and flat. My suggestion is to have a muffler shop make the crossover pipe. There are SO many variables, not the least of which is front driveshaft clearance. No pics, I'm waiting until after I swap in my 468 to mess with the exaust again. I have headers, dual 2 1/2" pipe into 1 chamber flows, 3" turndowns. Yes, it's loud. Yes, I like it. The exaust doesn't shake anything to compare with the vibration of 44's and wheels packed full of mud.
     

Share This Page