Rpm Specific Vibration

[JFortner5]

I’ve got a vibration that seems to come and go. It’s pretty much always there and sometimes I can feel it at idle. It mostly comes in around 1300rpm and is strongest around 1500, and seems to fade away ~1800. The truck is an 05 and has an NV5600. It doesn’t seem to be affected by load at all.

I first thought that maybe it was a u-joint or hanger bearing but since it’s happening in the same rpm range I’ve kind of ruled that out. They all feel tight as well. I thought maybe it could be an injector, but I would think if it was a miss I’d have it at idle and through the whole rev range. I’m also leaning away from that because it happens whether I’m accelerating or coasting and not giving it any fuel at all.

I’ve been reading up on replacing the harmonic damper. I know it should be replaced if rubber is missing or protruding, or if it has any wobble. I might have a tiny bit of rubber protruding but it’s not much. I can see a very slight wobble to it at idle. My truck does not have the smoothest idle but this is my first diesel and I’ve been told it’s pretty normal. I do believe my damper could be on its way out, but I’ve never really found anything about what kind of symptoms it causes.

The other thing I’m not sure about is if it could possibly be clutch or flywheel related. The previous owner had the clutch replaced, but I’m not sure with what. I do have the NV5600 so it should be a single mass flywheel. Is it possible to put a G56 clutch/ dual mass flywheel on an NV5600? I know 05.5 got the G56 so I was thinking if it’s possible maybe whoever put the clutch in messed up.

I know that’s a long shot and I’m going to install the 6.7 damper and see if it helps. I guess I really just wanted to know what happens when the damper stops doing its job.

Thanks,
Joey

 

[Topzide]

Is this vibration while driving or just sitting in the driveway? If happening while driving, does it happen on the same roads, different roads? If it seems to be happening while the truck is moving and you say it comes and goes, could be rocks and or debris in the tires. I know that I lost almost all vibrations while driving after adding Centramatic wheel balancers. Only start to have a vibration at 85 MPH! Used to have several different ones at different speeds. I would think that if it was the dampener, you'd have the vibration sitting still. Try to provide a bit more info, so that we can help narrow it down for you. Don't load the parts cannon yet!

 

[JFortner5]

I did leave out some important parts haha, I was in a hurry.

This is not just one road so I don’t believe it’s a tire. It’s more of a low frequency vibration or pulse. I do have a higher frequency vibration at idle but it’s not terrible and I believe it’s just normal diesel vibration, but that could be the damper. The pulse I’m talking about does feel similar to how a tire feels when it’s out of balance but it’s not related to speed it’s only rpm. It will do it sitting in the driveway if I rev it up to 1500rpm.

It’s either in the engine or something attached to it. My first thought was an injector and maybe it is, but it does it coasting downhill in gear when it’s not even fueling. The truck has good power, it starts easily and doesn’t smoke. The exhaust sounds smooth and doesn’t sound like it’s missing or anything. There’s no blow by either. It’s got 179k miles on it.

 

[Topzide]

While coasting without fueling, I'd say it's in the drive line. Bearings in the trans, u-joints or pinion carrier. Also check mounts for engine and trans for wear or cracks. I'd put the rear up on jack stands and have helper bring up to RPM to check condition.

 

[JFortner5]

It does it coasting but only in gear and the clutch engaged. If I push the clutch and the engine drops to idle it goes away.

 

[Ozymandias]

While coasting without fueling, I'd say it's in the drive line. Bearings in the trans, u-joints or pinion carrier. Also check mounts for engine and trans for wear or cracks. I'd put the rear up on jack stands and have helper bring up to RPM to check condition.

I don't think so as the vibration is there reving the engine without load parked in the driveway.

 

[Ozymandias]

If you suspect an injector put a bottle of power service in the tank and run it through. But usually a faulty injector also makes smoke.
But it's worth a try.

 

[JFortner5]

I’ll give it a shot. I just don’t know if maybe the damper is moving on the rubber or heating up and making it wobble more. I know it’s a damper and not a balancer so I don’t really know what happens when it starts failing. The guy before me seems to have taken pretty good care of the truck and he’s owned it since 2006. He said he had the valves adjusted pretty recently and the clutch replaced.

I might pop the valve cover next weekend and just double check the valves and see if anything looks out of the ordinary. I also like the idea of a helper, maybe I can get my buddy to rev it up while I’m looking at the damper.

 

[sag2]

Pull the belt off to eliminate any accessory drive.

 

[bcbender]

I can get my buddy to rev it up while I’m looking at the damper.

No need to rev and look at the damper, if you suspect its damaged, just check the alignment. there is a mark that'll be lined up if its good, also the rubber will be tight.

 

[RussellSullivan]

When parked in the driveway does the noise/vibration go away with the clutch disengaged?

 

[Blakers]

Early on the 3rd generation trucks had an rpm-related vibration from the hoses going to the hydroboost unit. Mine on my 03 was replaced by the dealer with a weighted hose that stopped the vibration.

 

[CharlesinGA]

Consider installing a Fluidampr. I saw that you mentioned the 6.7 damper but the Fluidampr has a bevel cut on the back to enable belt installation (old ones don't, but they would have to be four or five year old stock.

I'm not big on mods but if it truly works, I am all for it, this was the first mod I did.

Best price I could find in a quick search was $567 https://www.jegs.com/i/Fluidampr/388/920301/10002/-1 Boy have they gone up, I think I paid $318 for mine in mid 2018. Consider Genos also. https://www.genosgarage.com/category/s?keyword=920301 You probably would want to install new bolts, and I'm not sure you can get it in with the fan in place, I took the fan off first thing (36mm open end and a aircraft rivet gun with a flat set, gloves and a prybar to hold the heads of the pulley attach bolts. -OR- consider the Genos fan wrench kit. https://www.genosgarage.com/product/ram-cummins-fan-clutch-removal-wrench-set-gg-fc-wrenchset/tools)

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I can attest to the fact it makes a distinct difference in the feel and vibration levels of the engine, and the engine seems quieter too, all at least until you get accustom to it, then its normal. Damper on the left with the bevel is new, other is old. Verify with any seller than what you are getting has the bevel on it and the tone ring machined into it, and that it is fluidampr p/n 920301.

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[PLohr]

@JFortner5 :
You've definitely found some possibilities.

When I replaced my clutch, I took the new clutch and pressure plate assembly to have it dynamically checked and balanced. The shop found the assembly to be out of balanced by quite a bit. This is a large diameter, heavy assembly which could produce significant vibration.

This photo shows the new pressure plate and flywheel assembly with new weights welded on by the balancing shop:
https://photos.app.goo.gl/ECfgQuM52XSAEgQH6

A shop that dynamically balances rotating assemblies for engines should be able to check and balance your pressure plate and flywheel assembly.

Cornell Balancing in Fort Myers, Florida did my balancing work. They are very knowledgeable.

South Bend Clutch could improve some of their products by having them dynamically balanced. I've tried to communicate this to them.

You could also have your harmonic damper checked by a balancing shop. If you want to have an interesting conversation, ask them about balancing a Fluidampr.