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Advice needed: Flexplate area noise???

Discussion in 'The Garage' started by 78Buford, Sep 5, 2006.

  1. 78Buford

    78Buford 1/2 ton status

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    Yeah, it's a Ford, but I'm guessing that someone with a V8-Automatic combo has had a similar issue...I hope so, because I don't know the source of the noise.

    For the past month or so, I’ve been hearing a noise from my truck, and I don’t know what it is. Here are the symptoms:

    When going forwards, it makes no noise whatsoever. If you put the auto trans in reverse under load (backing up a hill or even sitting still holding foot on brake while applying throttle in reverse) it makes a sound similar to fan blades hitting metal....the sound seems to be coming from the torque converter/flex plate area. I am certain that the motor mounts are good (they are solid steel mounts), as the engine does not budge when placed under load in forwards or reverse. I’m sure that the fan is not hitting anything, as it has no shroud and is nowhere close to any metal objects. I’ve thought that if there was a problem with the flex plate, it would have to make the sound while going forwards...the flex plate and torque converter are always moving the same direction. Again, it only makes the sound while in reverse under load...it does it in 2wd and in 4wd.

    Any advice is appreciated.

    Thanks,
    Roy
     
  2. kennyw

    kennyw N9PHW Premium Member

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    It is probably a cracked flexplate. Very common problem and can make noises in one direction and not the other.
     
  3. mikey_d05

    mikey_d05 1 ton status GMOTM Winner

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    Messed up flexplate or loose TC bolts would be the easiest place to start looking.
     
  4. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    I second a broken flexplate. They usually break close to the bolt circle holding the flexplate to the crank so it makes it hard to view from the bottom but on most fords you can't see into that area anyways since they have a full round bell housing.
     
  5. 78Buford

    78Buford 1/2 ton status

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    After I posted, I went outside, started it (it is sitting on the trailer, strapped down at six different points, for a ride this weekend) and after a couple minutes, put it in reverse, applied brakes & throttle in reverse...it made the noise I mentioned. In forward gears, it was silent. I let it run for 5-10 minutes more, repeating this process. Never any noise going forwards, and after 10 minutes, it made absolutely no noise in reverse....with foot cramming on the brakes & heavy throttle in reverse...no "metallic/interference" noise whatsoever. I shut it off for 10 minutes or so, restarted it & repeated the process...no noise. I have noticed in the past that the noise seemed louder when the truck wasn't warmed up....but that makes absolutely no sense to me....unless something "self clearanced" which I kinda doubt.

    I'll do the same thing tomorrow & see what it does...

    Thanks for the replies.

    Roy
     
  6. 78Buford

    78Buford 1/2 ton status

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    I've had a few GM vehicles in which the torque converter bolts backed out of the converter....all the way out & were flopping around in the lower bellhousing area...the loose flex plate sounded like a rod knock under acceleration. The C6 in the truck has studs sticking out of the torque converter....nuts on the studs. I will start the truck (cold) tomorrow. If it is quiet in refverse under load, I'll leave it alone. If it makes noise again, I will pull the starter & trans inspection cover (bottom of the flexplate/TC area) tomorrow. What I'm bewildered by is why the sound happened tonight while the engine was cold, and not when hot. (I guarantee that the engine is not making the noise....it carries 80 psi oil pressure cold, and 30 psi @ 800 rpm hot....60 psi hot at 2000 rpm).

    Thanks again,
    Roy
     
  7. mikey_d05

    mikey_d05 1 ton status GMOTM Winner

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    Yeah, I'm an idiot and forgot that Fords use full bellhousings without a "dust cover". Sorry about that.
     
  8. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Perfect sense that the noise is there when cold but not noticable or gone when hot, signs of a broken flexplate for sure.
     
  9. readymix

    readymix 3/4 ton status

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    My 2002 Avy was doing the same thing up until today...guess what it was....







    Cat Converter was falling apart on the inside, who'da thunk it.
     
  10. 78Buford

    78Buford 1/2 ton status

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    Please explain.

    Thanks,
    Roy
     
  11. CB77GMC

    CB77GMC 1/2 ton status GMOTM Winner

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    Had what I thought was a lifter tick for awhile when I started cold. Once it was warm no tick. Well the front pump finally went out and had to drop trans and found center section of flex plate had lots of cracks.:doah: Pressure and heat will make weird sounds on a thin piece metal. Look around bolts in pic.

    flexplate (Small).JPG

    flexplate (Small).JPG
     

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