Cummins Vibration Damper

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Cummins Vibration Damper

July 28, 2014, 02:07:45 pm

After comparing my Cummins C8.3 vibration damper to the diagrams in my Operation and Maintenance Manual, it seems that my vibration damper is possibly no longer within spec or right on the edge of being out of spec as compared to the diagram on page 7-9. It certainly isn't in terrible condition but I'm starting my research on a replacement ahead of time.

Has anyone replaced theirs? Also, has anyone stepped up and gone with a viscous fluid damper, such as Vibratech or Fluidampr, rather than a rubber impregnated one like the original? It looks like all the modern Cummins engines have come with a fluid damper as OEM and they don't use the rubber ones anymore.

Here's a link- TDR 73: It's Time to Check Your Cummins Harmonic Damper

Re: Cummins Vibration Damper

Reply #1 – July 29, 2014, 09:04:32 am

Which way are you leaning - stock or 2 to 3 times the price for aftermarket?

Cummins 8 3 Harmonic Balancer | eBay

Cummins 3925570 Damper Harmonic Balancer Genuine C8 3 6L8 9 ISC8 3 QSC8 3 | eBay

Re: Cummins Vibration Damper

Reply #2 – July 29, 2014, 10:53:11 am

I'll probably go with one of the aftermarket ones.

The aftermarket ones seem to like they are supposed to last for the lifetime of the engine whereas the rubber ones will need replacement again (possibly more times depending on how long you have the vehicle).

Also, I'm curious enough about the vibration reduction and overall smoothness to give it a try.

Re: Cummins Vibration Damper

Reply #3 – July 29, 2014, 12:06:39 pm

Go for it! I'm sure you will post your results - I'll be curious to hear if it makes any discernible difference in engine idle "smoothness" (not a term I usually associate with diesel engines), although these type devices are more aimed at higher RPM vibration reduction. I like the Fluidampr construction and engineering.

Re: Cummins Vibration Damper

Reply #4 – July 29, 2014, 12:59:17 pm

The manual that came with my '95 M11 said to change the vibration damper at 10 years.
I asked at Cummings about that, he asked if it was leaking? No, then he said he wouldn't change it. I didn't however I always wondered if the old hard rubber dampened as good as it did when it was new and soft?
The damper is on there to protect the crankshaft from vibrations created when the engine is running.
A damper cost would be a lot less than a broken C/S if it ever came to that.
Google "Engine Vibration Damper", lots of info on this.

Re: Cummins Vibration Damper

Reply #5 – July 29, 2014, 01:29:37 pm

Quote from: John Duld – July 29, 2014, 12:59:17 pm

The manual that came with my '95 M11 said to change the vibration damper at 10 years.
I asked at Cummings about that, he asked if it was leaking? No, then he said he wouldn't change it. I didn't however I always wondered if the old hard rubber dampened as good as it did when it was new and soft?
The damper is on there to protect the crankshaft from vibrations created when the engine is running.
A damper cost would be a lot less than a broken C/S if it ever came to that.
Google "Engine Vibration Damper", lots of info on this.

I'm assuming that yours has the rubber ring like the one in my picture and that the mechanic was incorrect about your damper being a fluid filled one. If yours has the rubber ring, is the ring in perfect condition and not starting to fray or deform or stick out on an edge? The diagrams show that the rubber should be completely uniform around the whole thing.

I would be curious if you (and Cajk or anyone else) could post up a picture of yours since your coaches are a few years older than mine and would be presumably in worse shape. I know Cajk has about 50% more miles on his coach than mine.

Re: Cummins Vibration Damper

Reply #6 – July 29, 2014, 01:52:14 pm

Robert,
I sold my coach a few years ago so can't go have a look but don't think it had the rubber ring on it.
Maybe you can see one on an early (Around '95) M11.
On an over the road truck by the time it's 10 years old it has probably been through an overhaul and got a new damper.
As some of these motor homes get up around 15 or 20 years old it might be something to replace?

Re: Cummins Vibration Damper

Reply #7 – July 29, 2014, 06:17:47 pm

If the balancer is concentric when it's running and the isolator (rubber insert) looks good & your picture looks good, I'd have a problem fix'n something that ain't broke.

When the insert rubber starts to split in the direction of travel is when a balancer is needing replacing.
DamperDoctor if you are frugal.

Look at a new one for comparison. pc

Re: Cummins Vibration Damper

Reply #8 – July 29, 2014, 07:19:44 pm

Robert,

Here's the best I could do on photos. I have 164,000 miles and 3900 engine hours. I think I see some of the same "extrusion" you are seeing. I can't tell from my photo if the alignment marks have shifted - need to get them around to the top for a better look.

Re: Cummins Vibration Damper

Reply #9 – July 30, 2014, 01:26:48 am

Chuck, is it possible to send those photos to a cummins shop and get their take on the condition of the balancer? Just a thought.
Richard B

Re: Cummins Vibration Damper

Reply #10 – July 30, 2014, 08:34:26 am

Our local Cummins service facility is too busy with oilfield trucks to bother with RVs. Anyway, after seeing photos of still running engines where big chunks of rubber are missing from the balancer, I'm not too worried about mine. I will wait for Robert to take the lead (and spend the cash) in trying out a aftermarket solution. If he has good luck, then I'll replace mine.

Re: Cummins Vibration Damper

Reply #11 – July 30, 2014, 09:56:28 am

I won't do it this year but was mostly just seeing if anyone has changed it out. It'll be kept under observation and possibly next summer changed out. (I've still got to take the tranny in for vertical movement of the damper which I noticed when I was greasing the u-joints. Always something going on.)

Re: Cummins Vibration Damper

Reply #12 – July 30, 2014, 01:37:55 pm

A good quick check would be to mark the inter and outer on the vibration damper, then check it from time to time to see if your marks still line up, if not
then it would be time to replace it.

Crazy J
2002 Foretravel U320
2009 HHR

Re: Cummins Vibration Damper

Reply #13 – July 30, 2014, 08:08:00 pm

The damper actually comes (when new) with index marks scribed on the front side. You can see them in one of my photos. I just can't tell (because of the angle) if they have moved...I will get out tomorrow and bump the starter until I get them to where I can see them more clearly.

Re: Cummins Vibration Damper

Reply #14 – July 31, 2014, 02:27:37 pm

Well, after calling Vibratech, they didn't seem to have any clue about the C8.3 application and told me to contact Pittsburgh Power, who also had no clue.

I'm looking into whether the ATI Super Damper ISC application will work on the C8.3 and researching bolt patterns, etc. Hard to believe that with all these 8.3s used in all kinds of different application from boats, ag equipment, generators, etc. that nobody seems to know anything about a replacement vibration damper.

Re: Cummins Vibration Damper

Reply #15 – August 01, 2014, 06:14:44 pm

Here's mine 75,000 miles 1998.

Re: Cummins Vibration Damper

Reply #16 – August 02, 2014, 10:00:40 am

Not too sure what sort of an answer is being looked for with this OP ?

Most generally diesels have ((very)) little issue with harmonic balancers.

If on the other hand you are at the local drag strip with your MH, running it
through its paces you may encounter issues after several seasons of competition.

Proper running diesels operate smoothly and are not beat on (especially with Allison transmissions.) pc

Re: Cummins Vibration Damper

Reply #17 – August 02, 2014, 10:09:35 pm

They are technically (I *think*) torsional dampers. The longer the crankshaft is (straight 6 vs v8) the more there is a need to dampen torsional resonances that can occur. Ensuring no torsional resonances occur throughout the operating conditions of the engine is not an easy task.

With that said. It don't look broke, so why worry? There's a LOT of 8.3's out there on trucks that get fair less care than we give ours.

Re: Cummins Vibration Damper

Reply #18 – December 12, 2014, 01:41:56 pm

Update.

We have a very different crankshaft/vibration/harmonic damper than probably 90+% of the Cummins C8.3s out there due to the mounting of our hydraulic pulley system. All of these applications that list a crankshaft damper for an C8.3 or ISC don't have the extra holes for the mounting of that front pulley setup that we use. This rules out pretty much every non-stock damper being used on our engines.

I actually bought a used non-stock viscous damper that was listed for a C8.3 for $120 just to see if it would be able to work and it is clearly not set up for our applications. It would take a lot of work at a machine shop to adapt it (which I may end up doing or trying to rig up something myself with it).

In the end, I replaced my vibration damper with a replacement unit from here-

DS-3925566 | Cummins Crankshaft Damper | 6C | ISC

which end up being an approved equal from this company

PAI Industries, Inc. - Part Search Result

Seems like a nice product and removed a bit of the wobble that the old damper had and the engine runs a bit smoother. After seeing how the rubber torsion ring looks on a new unit, mine was definitely not in spec anymore and I'm glad I replaced it.

Re: Cummins Vibration Damper

Reply #19 – December 12, 2014, 02:25:49 pm

Robert,
For $130 that was probably a good move.
I think Cummins wanted $400 for the one for my engine so I never changed it. At five years past the recommend replacement time I always worried about that.
You don't have too!
JD

Re: Cummins Vibration Damper

Reply #20 – December 13, 2014, 07:54:26 am

Some of the FoFum members may remember that Jeff and Carol S had a 93, U225 (Rear Radiator) several years ago where the Harmonic Balancer came apart while traveling in West Texas. The outer ring got up into the cooling fan and destroyed it. Somehow it did not hit the CAC or the radiator but fan parts were found all over the engine compartment and even back on the hood of their Jeep towed. The outer ring landed and was found on the rear coach frame.

This was the first time I had ever heard of one coming apart. The Belts had just been changed by both FOT and worked on at a Freightliner dealer so there was apparently no sign of the pending failure. Keep in mind that being a rear radiator unit visual inspection would be pretty tough.

Just keep in mind that harmonic balancer failure can be pretty serious. They had a $1200 tow, bill covered by Good Sam, and we all spent about a week in Fort Stockton, TX awaiting parts and repairs.

Re: Cummins Vibration Damper

Reply #21 – December 13, 2014, 09:02:33 am

FYI, I had a wobble in my pulley that drove the hydraulic pump. It would cause the tensioner to bounce. I first thought the pulley was bent due to a wack with a hammer, etc. A little bit of measuring with an indicator showed it was the plate that the pulley mounts to. Details here: Part Number? Crank Pulley that drive hydraulic pump

Re: Cummins Vibration Damper

Reply #22 – December 13, 2014, 09:04:37 am

Quote from: rsihnhold – December 12, 2014, 01:41:56 pm

Seems like a nice product and removed a bit of the wobble that the old damper had and the engine runs a bit smoother. After seeing how the rubber torsion ring looks on a new unit, mine was definitely not in spec anymore and I'm glad I replaced it.

What do you mean out of spec? Did the outer ring not line up to the inner ring? Do you have pictures?

Re: Cummins Vibration Damper

Reply #23 – December 13, 2014, 02:30:07 pm

Most of tensioner bounce comes from pulley misalignment with the belt constantly changing its pathway length many times per second as it jumps on the tensioner idler pulley. The crank pulley, tensioner idler and the hydraulic pump must be in exact alignment as well as the angles must also be the same.

Pierce

Re: Cummins Vibration Damper

Reply #24 – December 16, 2014, 07:05:28 pm

Krush,

The rings still line up (maybe very slightly off) but the rubber damper portion is no longer flush all the way around. It is sticking up 1/16" or so about half way around and flush (the way it should be) the other half. The Cummins maintenance manual that came with my FT states on Page 7-9 that if portion of the rubber damper isn't flush with the metal surfaces or close to it, it needs to be replaced. I don't know if this manual got passed on to you by the PO?

The new damper has the rubber entirely recessed all the way around.

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