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Nasty sickning grinding sound after hard acceleration

Discussion in 'The Garage' started by laketex, Jan 11, 2004.

  1. laketex

    laketex 3/4 ton status

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    Ok...gotta question. After hard acceleration (usually in 3rd gear on my 4-speed), my truck has started this low vibration, high grinding sound. Hitting the clutch or brakes does not stop this phenomenon. The only thing that stops it is stopping the truck completely. After this, it won't act up again till I wrap the truck up again. I wish I could describe the sound, but it sounds like metal on metal, and it's constant, not like something is hitting something else over and over...instead, it is a long constant harsh sound. Other than this, the truck runs and drives perfect. If anyone has some hints as to why this may be happening, please give me a heads up. I'll try to get dan on here with his description as well cause he was in the truck yesterday as it happened. Thanks. This is really stumping the 2 of us.

    Bryan
     
  2. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Can you hear where it's coming from at all?
     
  3. jimmyjack

    jimmyjack 1/2 ton status

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    I was gonna say it's a flex plate but you mentioned a clutch. What about a spring on the clutch plate?
     
  4. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    I was gonna say it's a flex plate but you mentioned a clutch. What about a spring on the clutch plate?

    [/ QUOTE ]

    I would say it's nothing to do with that if stopping with the engine idling makes the problem go away. I'd guess it's probably in the transfer case, driveshaft, or rear axle, but it's hard to say without hearing it.
     
  5. ben427

    ben427 1/2 ton status

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    a fellow up here had a similar prob in his jeep with and NP435 and his tranfer case adapter was loose and ready to fall off.
     
  6. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Bryan-

    I vote for a good round of fluid checks on EVERYTHING, re-torquing down bolts on all driveline parts, and lifting the front axle to check for loose parts. The only things changed while it was gone was the tierod, wheel hub, and exhaust.

    Hope Tyler doesn't mind /forums/images/graemlins/grin.gif, but here is a conversation we had to rule a few things out:

    Tyler: i think its his exhaust making his noise, what do you think
    Dan: I dont think so
    Dan: it doesnt have to do with RPM at all
    Dan: its wheel speed
    Dan: really an odd noise
    Tyler: his exhaust could be hitting the driveline
    Dan: nope, thats not it
    Dan: or it would rub all the time
    Dan: when he rips on it
    Dan: but it does not
    Tyler: he said it didnt start until he got the exhaust
    Dan: that is true
    Dan: HOWEVER
    Dan: he also had that groove cut in the pass. front hub
    Dan: and the tie rod "straightened"
    Dan: I highly doubt its the exhaust
    Tyler: could it be mild DW
    Dan: nope
    Dan: I was in the truck once
    Dan: when it happened
    Dan: there was no abnormal shaking
    Dan: or vibes
    Tyler: so what did it sound like
    Dan: almost like bearing or gear chatter
    Dan: pretty damn loud
    Tyler: something in the 205 maybe
    Dan: just when it happened, I had him depress the clutch, and let the motor idle down
    Dan: no change
    Dan: maybe
    Dan: He should check gear lube levels
    Dan: its really odd
    Dan: he says it only does it after he rips on it
    Dan: BUT
    Dan: it doesn't do it if you just rip 1st
    Tyler: 265 could be messed up then
    Dan: if you get off of it then, and ride 2nd normally... no noise
    Dan: but he ripped 1st and 2nd, and thats when it happened
    Dan: the noise stopped once we dropped below ~5mph
    Tyler: maybe like a main or countershaft bearing
    Dan: I wouldn't think so...
    Dan: that 465 was SO tight
    Dan: unless its OUT of lube...
    Dan: I couldn't see it making that noise...
    Tyler: clutch problem then maybe
    Dan: possibly... but only after 2nd above 4000rpm?
    Tyler: hell if i know then
    Dan: lol
    Dan: I think he should check ALL his lube levels
    Dan: the damn thing took 2q of oil when we picked it up
    Dan: in the motor
    Dan: but the 465/205 really doesn't leak anymore...
    Dan: the cuz would have had no reason to drain either
    Dan: we did install his 2nd hub last night
    Dan: I wonder if its happened again since


    Hope that helps Bryan!

    -Dan
     
  7. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Tim-

    It sounds like its coming from directly under the seats... trans/xfer or perhaps slightly forward of there. Its a pretty loud noise, and with no carpet or anything, it really reverberates inside the truck, making it difficult to pin point.

    -Dan
     
  8. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I personally think you're right in thinking it's in the transfer case then. The clutch doesn't stop spinning when you stop the vehicle, but the transfer case does, as does everything behind that. That's where my thinking came from that it's not in anything forward of that, which turns all the time when the engine is running.
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    No chance it's your speedometer cable? I ran into an issue where it was rubbing the floor when I was moving because it wasn't fully supported/secured.

    Probably not LIKELY, but the speedo stuff is also something that doesn't stop moving until the vehicle does.
     
  10. laketex

    laketex 3/4 ton status

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    no way...this is more...substantial than that. I hate trying to describe noises /forums/images/graemlins/blush.gif

    I'll go under the truck tommorrow and check everything out pretty good, fluids, and all that.

    Bryan /forums/images/graemlins/confused.gif
     
  11. Confedneck

    Confedneck 3/4 ton status

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    throwout bearing?
     
  12. 71RestoRod

    71RestoRod 1/2 ton status

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    Have you tried popping the 205 in neutral while it's acting up? It seems like doing that would relieve any binding on the trans output shaft and might tell you if it's the 465.
     
  13. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Strange thing is that we just dropped that 465/205 in the truck! The trans, output shaft, sleeve, input shaft and 205 were all tight when we put them in...

    I don't see why it would be giving him problems now.

    -Dan
     
  14. laketex

    laketex 3/4 ton status

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    funny you bring this up. For a while there, I was getting a loud bang when I'd let off the clutch in 1st gear. Somebody mentioned throwout bearing there too, but the bang noise went away and I'd kinda forgotten about it. Good option.
     
  15. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    funny you bring this up. For a while there, I was getting a loud bang when I'd let off the clutch in 1st gear. Somebody mentioned throwout bearing there too, but the bang noise went away and I'd kinda forgotten about it. Good option.

    [/ QUOTE ]

    I don't really think so. You said the sound only stops when you stop the vehicle, and that it doesn't change when you step on the clutch. I'm still pointing to something further back, and I really don't think my logic is flawed on that one.
     
  16. Mudzer

    Mudzer 1/2 ton status Author

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    Well, you've done the process of elimination. We can pretty much eliminate anything from the bellhousing forward since its not an RPM derived noise. It has to be somewhere from the transmission down to the axles.

    Simple things first. Do you have the NP205 out of 4wd? Do you have drive flanges or lockouts? Are they locked out or can you remove the drive flanges to listen for a noise? Reason being, you could have a bad joint in the front shaft or could the reason be your rear driveline angle? If you ever rode in my truck right after the doubler install, it would have scared ya! I had a very bad grinding noise on deceleration. Sounded like two gears barely touching. I thought it was a problem in the cases. I had people riding with me with their ear on the NP203 box that stuck through the floor. "Yup, thats the problem" we said. We thought the idler was out on my newly rebuilt doubler! This is why I trailered mine to Hot Springs in 2003.

    Anyway, I traded many emails with Steve Sharp and he narrowed down the problem to "gear clatter" in the t-cases. The problem was the rear driveshaft angle was so severe and required a CV. He told me the driveshaft was developing harmonics and transfering these vibrations into my t-case. This happens with almost any lifted vehicle with severe driveline angles that do not have a CV. I have even heard of an NP208 having the same problem and its a chain case!

    Your vibration could be excited by the "whomping" and extreme acceleration. It doesn't matter if you clutch it, the vibration remains because the driveshaft is spinning the gears inside your case. This is the very instant the noise is made. Mine was so severe, I had it during deceleration as well as at cruising speeds. At speed, it would develop quickly but a very low pitch. The pitch would eventually get higher and louder until I was literally plugging my ears while driving! Consider a CV in the rear, this might fix your problem.

    It would be a real simple test if Dan was willing. Remove Dan's CV shaft from the rear and purchase your own 1330 CV yoke and seal. Install the yoke and seal on your rear output shaft, then "borrow" his "SHAFT" for a little cruise. If that cures it, you need to buck up and buy a CV shaft! /forums/images/graemlins/thumb.gif
     
  17. backyardbuilt

    backyardbuilt 1/2 ton status

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    I'll second that mine made a terrible noise just like that and would stop when you stopped the truck and not come back for a week then come back just for the hell of it.
     

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