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Clattering with light load


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So I have an issue that's been going on as long as I've owned this truck, it's a e6 350 with a maxitorque 9 speed. Between 1200 and 1600 rpm I hear a distinct clatter but only under light load and the truck has to be in gear and rolling. When I rev it up in place at that RPM range It won't make the noise at all, and when I'm pulling a heavy load and get into it, it goes away also. Sounds a little too loud to be an injector knock. Oil pressure is around 30 at idle, 60psi at 1600, 90 at 2100 and oil is clean. Just put a headgaskets in it and cylinder walls look great, all still have crosshatching and no scoring. This noise almost sounds like it's coming from the rear of the engine or more like the bellhousing/clutch. Sounds like it's right under the cab when I'm driving. I'm not sure where to start. 

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I have had the auto power divider send a sound through the drive shaft, imitating a tranny issue. could this be what you hear? (assuming you have an auto power divider)?  jojo

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1 minute ago, Lukasswaziek said:

Yes truck has 2 pto's 

if it were the older style spicer clutch they would clatter while you stepped on pedal. no noise parked with 1600 rpms would indicate trans counter shafts aren't moving 100%. under light load ( possibly even bob-tail) has light load on drive train allowing for free style back lash. under HD load the drivetrain is tight under load ; no back lash. far as the PTO question; ! -1 == one of them not engaged ( that was brought up in another text), 2== have you checked back-lash  in the PTO's? if they or at least one is a side mount  under light load moving the drive gear would be turning. rear mount hyd  shouldn't be that noisy.

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18 minutes ago, Joey Mack said:

ok.  can you sneak a thin bar into the tranny inspection hole and see if you can move the input shaft, side to side..  have someone hold the clutch 1/2 way down,  use the bar to see if the input shaft is sloppy..  heck look at the throughout bearing for excessive wear or possibly see a ring spinning on the shaft between the throughout bearing and the clutch brake, if it's still there,,  I think you have a spring loaded clutch brake in that old gurl...  Jojo

just a thought Joey; if it were the clutch brake or pilot bearing the noise would be there parked and running 1600 rpm's . should'nt make a difference with load weight ?? that's why i thought more toward gears moving or PTO malfunction. ????

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I guess i was thinking a bout a wobbling input shaft when running.  and I have seen many broken throughout bearings..  and input bearings rotating like a small football..  however,  I can alway's use a little education..  :)  it's tough to diagnose on the phone... so-to speak...  jojo

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agree 110%. see and physically hear  make a better diagnostic determination. still good to try and be helpful not to mention keep the ole brain cells active...LOL i'd be interested in the PTO set ups.

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for sure on the PTO's..  There could be one staying engaged or just f'd up..   for sure.. i would expect a pto noise to increase as you rev up or drive,  ...  glad to see you on this one 'Mech'   jojo

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also we don't know if when truck is at stand still reving up to 1200-1600. is the driver keeping his foot on clutch pedal or neutral  and pedal up ??  "but doctor i don't feel good" -- what hurts----   I don't know  but it hurts 😄

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7 minutes ago, Joey Mack said:

for sure on the PTO's..  There could be one staying engaged or just f'd up..   for sure.. i would expect a pto noise to increase as you rev up or drive,  ...  glad to see you on this one 'Mech'   jojo

depending on PTO set up , as earlier stated light load less engine noise /more free float gears, heavy load more fuel== more engine noise & less backlash. if it were an engaged pto i would think there would be an over heat smell  from hot pto 

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1 hour ago, Lukasswaziek said:

I don't think so. I can't feel a driveline vibration and if it was a tranny issue it sounds like it's at the front of the transmission

a worn power divider will send a noise through the driveshaft tube into the trans with out causing a vibration. did you try jacking up one side ;;chock blocks and every possible safety feature. put unit in gear slowly bring up the rpms with LIGHT pressure on brake to put resistance on drive line?

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Okay so got the read ends on jackstands, front wheels blocked. Put it in a higher gear and would drag the brakes and now I'm leaning more twords the engine making the noise. It sounds like a real bad injector knock, but for some reason just resonates in the cab. but then again I'm not hugely familiar with Mack trucks and the noises they make. Mostly worked on and drove cats and cummins. I checked the pto's to see if either one was making the noise and it's not that. If you get it at the right rpm it sounds more like a hard knock rather, but otherwise clatters with the engine firing

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pull the valve covers and look for really sloppy rocker arm's...  do you know how to rotate this engine to check each cyl. ?  no offense here, just need to know.. jojo

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1 hour ago, theakerstwo said:

What was the reason for replacing head gaskets and did you have  fire ring blowed in one of the gaskets?

While it was making that noise and bothering me, I was searching for what It could of been, and there was a small amount of antifreeze leaking from the headgasket that I hadn't noticed before so I suspected that it was a compression leak noise, but it wasn't. No compression passing by the fire rings anywhere. The gasket was weak in a corner though

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8 minutes ago, Joey Mack said:

pull the valve covers and look for really sloppy rocker arm's...  do you know how to rotate this engine to check each cyl. ?  no offense here, just need to know.. jojo

Yes just adjusted the valves, no difference

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1 hour ago, Lukasswaziek said:

Okay so got the read ends on jackstands, front wheels blocked. Put it in a higher gear and would drag the brakes and now I'm leaning more twords the engine making the noise. It sounds like a real bad injector knock, but for some reason just resonates in the cab. but then again I'm not hugely familiar with Mack trucks and the noises they make. Mostly worked on and drove cats and cummins. I checked the pto's to see if either one was making the noise and it's not that. If you get it at the right rpm it sounds more like a hard knock rather, but otherwise clatters with the engine firing

keep in mind these questions might sound simple ; it's a challenge not being there . are you by yourself listening or are you doing the walk around while someone else does the fuel pedal/ brake application? what happens with 1200-1600 rpms and No brake pedal. trying to narrow down possiblities. went from a maybe clutch/ driveline  to engine . have been there done that on site frustrations with  noise or vibrations. the distant diagnostic has many more  options

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Mechohaulic I have someone here operating the brake while I listen, and when no brake is being applied you can hear it in the cab but it's quiet, when you push on the brake it gets louder until you pass that RPM range. When I listen next to the engine, I can hear what sounds like the same clatter but not as distinct as when sitting in the cab. Believe me this is frustrating. If I could pinpoint it easier it would not be as frustrating. I've worked on trucks my whole working career, and this one is making me really scratch my head

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Well have just read thru this and this is what I understand from what I have read

Noise is believed to be coming from the back of the engine or front of the transmission 

Only happens in gear with a light load

If it was mine I think it would be time pull the transmission back if its a concern

But I  would check the endplay on the crank first to make sure it isn't floating to much and allowing something to just touch somewhere 

It has gotta be something pretty simple going on

The transmission shafts have a fair bit of float forwards and back as I feel the crank

 

Joey will probably have the specs at hand for the crank float and the transmission, well it will be what it will be, they are a pretty agricultural transmission but tough as nails 

 

Paul 

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