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Crap, knocking

Discussion in '40- & 55-Series Tech' started by 76BigheadFJ40, Jul 31, 2005.

  1. 76BigheadFJ40

    76BigheadFJ40

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    So I was driving today when out of the blue I start to hear a knocking. investigate a little further and it only occurs when I am in gear and at the top end of it. does it in all four gears. I have heard this sort of knocking before in a buddies ranger, but it was only in fourth gear and it was the entire way through. This knocking is only at the top end, so Im thinking, clutch? Maybe? I recently got an H41 and Atlas, so i will be extremely set off if it is either of those guys. Thanks for the help!
     
  2. Romer

    Romer fatherofdaughterofromer Moderator

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    Several questions:
    1) To clarify, if your at the top end and it knocks and you shift into nuetral, does it go away?
    2) Does it sound like it is in the engine or Tranny?
    3) Does it sound like a piston knocking?

    Might be fuel, bad gas etc. Hard to tell from here. Thats the cheap one. Get some of that stuff that gets water out of gas and try running a tank of higher octane and see if that does anything.
     
  3. Pin_Head

    Pin_Head

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    A better description would help. Does the knocking vary in speed with engine RPM or truck speed? Does it knock sitting still in your driveway?
     
  4. 76BigheadFJ40

    76BigheadFJ40

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    it knocks at the higher RPMs of the engine, only in gear. When I shift out, it stops, so yes. the sound comes from below, but, with the top off, you can't really tell exactly where. No, it doesn't knock in the drive way. The knocking gets faster and the engine screams more and more, but you have to really be listening. I would kind of guess piston, but because it is not the entire way through the RPM range, that kind of makes it a no. Something loose? anywhere?
     
  5. Pin_Head

    Pin_Head

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    I'm not really sure what you mean about my question of how the sound relates to engine or truck speed. I meant does the knocking get faster with truck speed or with engine speed. Since it doesn't do it when it is sitting still (presumably you rev the engine up to the same speed during this test) I assume it varies with the truck speed. This would suggest something on the outpus shaft side of the tranny, but this doesn' make sense with what you said about it only making noise at high engine RPM. It also doesn' make sense that the noise would go away when you take it out of gear (presumably at the same engine RPM where it sould have been knocking in gear).

    Sorry, I'm still confused about the noise and when it happens and what circumstances. I wish I was there to hear it myself. If you just installed the tranny and transfer and the noise is coincident with this, my best guess is that it has something to do with the new parts.
     
  6. 76BigheadFJ40

    76BigheadFJ40

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    sorry if I have been confusing, but it is a little hard to describe since it isn't a run of the mill knocking. today I realized that it is also doing this at about midrange RPMs as well, so I am sort of assuming that it does it in the lower area, but I just can't hear it. The noise does stop when shifted out of gear, and it gets faster as the RPMs go up. I am kind of leaning toward something loose dealing with the clutch, but I'll let you guys know as things progress.
     
  7. Pin_Head

    Pin_Head

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    It is strange.

    Just a WAG, but take the clutch inspection cover off and check if the flywheel or pressure plate is loose and wobbling (eg pry it back and forth). Also check the end play of the crank shaft by prying it back and forth at the flywheel.
     
  8. MDH33

    MDH33

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    Do you think that your exhaust manifold has developed a leak? That usually sounds like a knock that varies with RPMs.
     
  9. 76BigheadFJ40

    76BigheadFJ40

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    yeah, see, that is what my buddies think too, exhaust leak. i'm going to patch it up (if there is one) today and hope it works. We'll see
     
  10. Pin_Head

    Pin_Head

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    Exhaust leaks get louder with engine load and will be most noticible at full throttle and low speed in 4th gear, like going up a grade.