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LT's beating on underbody.

This is a discussion on LT's beating on underbody. within the External Engine forums, part of the LSx Technical Help Section category; I'm sure this is pretty common with LT's, and with 3 inch pipes I get a nice vibration when the ...

  1. #1
    Mad Fabricator Z34LS1's Avatar
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    92 LS1 Lumina A4
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    LT's beating on underbody.

    I'm sure this is pretty common with LT's, and with 3 inch pipes I get a nice vibration when the motors under a load.

    Short of crushing the 3 inch stainless Y pipe what fixes have you guys done? Steel mounts?

    This is the drivers side.
    Thanks for replying.

  2. #2
    Member goof4080's Avatar
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    A lot of guys add another spacer. Glad to see the Z34 LS1 again! I read your build years ago. And loved your vid. Have I missed any updates? I see you're blue now. Looks good!

  3. #3
    Member goof4080's Avatar
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    Quote Originally Posted by goof4080 View Post
    A lot of guys add another spacer. Glad to see the Z34 LS1 again! I read your build years ago. And loved your vid. Have I missed any updates? I see you're blue now. Looks good!
    I mean another hanger for the y to space it away

  4. #4
    Mad Fabricator Z34LS1's Avatar
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    92 LS1 Lumina A4
    00 Formula WS9

    You lost me, I think I explained it wrong. It's the drivers side header where it dumps.
    I have about a quarter inch clearance but when it torques up it hits.

  5. #5
    James Bond Spikito's Avatar
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    Someone makes a hanger that goes around the drivers side of the y-pipe, and bolts it to the underbody, to that it cant torque back and forth. Ive heard good things about it and planned on ordering one today, if i could remember the name

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    James Bond Spikito's Avatar
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  7. #7
    Spaz is My Mentor SMWS6TA's Avatar
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    Sounds like the drivers side engine mount is going.

  8. #8
    None Shall Pass Knight's Avatar
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    Quote Originally Posted by SMWS6TA View Post
    Sounds like the drivers side engine mount is going.
    It's worth checking.

    You should be able to brace the piping so it doesn't hit. Or switch to a solid motor mount.

  9. #9
    Mad Fabricator Z34LS1's Avatar
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    Quote Originally Posted by SMWS6TA View Post
    Sounds like the drivers side engine mount is going.
    Very good possibility. I will for sure be looking at it tomorrow.
    The bump stops sound cool Spikito, time to do a search.

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    Former Mopar Man 2002ssslp's Avatar
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    Mad Fabricator Z34LS1's Avatar
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    92 LS1 Lumina A4
    00 Formula WS9

    Well I'm stuck along side a road!
    Bad storms went through and traffic was bumper to bumper.

    Never went above 210 but as I got going again it cooled to 160 and it was like my throttle stuck at 2500 or so.
    so I had to shut it down. Brakes were working hard to hold her back.

    ANY IDEAS? it's dark but I got a flashlight and cannot see any broken or unplugged vacuum lines.

  12. #12
    None Shall Pass Knight's Avatar
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    Throttle cable sticking, or throttle body not closing completely?

  13. #13
    Mad Fabricator Z34LS1's Avatar
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    92 LS1 Lumina A4
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    Throttle cable is hitting its stop.

  14. #14
    Mad Fabricator Z34LS1's Avatar
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    92 LS1 Lumina A4
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    I did an EGR delete about a week ago, maybe something in the hole where the tube went behind the throttle body.

  15. #15
    Spaz is My Mentor SMWS6TA's Avatar
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    you sure you hooked it up all correct? PCV tubing should be going into the intake NOT the throttle body. The hose that comes off the throttle body should connect to a vent tubing on the passenger side valve cover.

    If that was backwards that could be causing the problem.

  16. #16
    Mad Fabricator Z34LS1's Avatar
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    92 LS1 Lumina A4
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    Quote Originally Posted by SMWS6TA View Post
    you sure you hooked it up all correct? PCV tubing should be going into the intake NOT the throttle body. The hose that comes off the throttle body should connect to a vent tubing on the passenger side valve cover.

    If that was backwards that could be causing the problem.
    The hose coming off the left side of my TB goes to vent on passenger side valve cover, the hose below it in the Intake Bottom hose goes to pcv lines, Sorry my Mistake.
    Last edited by Z34LS1; 07-02-2012 at 08:15 AM.

  17. #17
    Member Redrokit8's Avatar
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    In my case the Torque Arm relocation bracket was just kissing the exhaust near the "Y". I cut a small triangular wedge off the rear of the bushing mounting and noise disappeared. It was very hard to diagnose due the slightly changing pipe going from cold to hot. It didn't look like a problem until I got directly under the mount. That was in my case and there are probably a million more areas it can happen.
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  18. #18
    Mad Fabricator Z34LS1's Avatar
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    Quote Originally Posted by Redrokit8 View Post
    In my case the Torque Arm relocation bracket was just kissing the exhaust near the "Y". I cut a small triangular wedge off the rear of the bushing mounting and noise disappeared. It was very hard to diagnose due the slightly changing pipe going from cold to hot. It didn't look like a problem until I got directly under the mount. That was in my case and there are probably a million more areas it can happen.
    I had to Cut the rear bracket off the 3" Y Pipe then modify the Original to get the Factory Rear Hanger that slides into the Rubber mount to work, then welded the original back on.

    My Vibrations are minimal, and as stated above....

    Originally Posted by SMWS6TA
    Sounds like the drivers side engine mount is going".

    I think he's right, it's not broke but when I put it in gear it moves more than when I rev it, or at least when it's in gear then torques is when I get a little vibration.

    So Far I have not had to Flat Spot the Y Pipe but the sound feels like it's under my feet. When Accelerating Hard then Shifting the noise is much louder.

    I'm going to do the mounts next.

  19. #19
    Junior Member tdevil55's Avatar
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    I have hooker LTs and am getting the same thing. Mine is hitting on the k member where it connects to the a arm driver side. I just finished doing stock mount replacements and tranny mount, and it is still hitting, hit real hard when I put it in reverse. I am thinking of doing the umi solid mounts later this year and see where it gets me and see if I can get the clearance for the header. Last option is to either dent the header where it hits the k member or trim the k member off to clear the header.
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  20. #20
    James Bond Spikito's Avatar
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    Quote Originally Posted by tdevil55 View Post
    I have hooker LTs and am getting the same thing. Mine is hitting on the k member where it connects to the a arm driver side. I just finished doing stock mount replacements and tranny mount, and it is still hitting, hit real hard when I put it in reverse. I am thinking of doing the umi solid mounts later this year and see where it gets me and see if I can get the clearance for the header. Last option is to either dent the header where it hits the k member or trim the k member off to clear the header.
    both of those have been done many times

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