Vibration/Harmonic question

[TO'Brien]

My truck has a Vibration/Harmonic that at it’s worst at 72 mph.



I have read a lot of the threads that have talked about vibration:

Drive-line angle

How tight the parts are

Replacing shafts

A/C issues

Dealer problems



I have visited the dealer. They worked the problem so that the truck had over 30 days of down time to cover New York States lemon law. They also got DC to say it normal for a truck to vibrate; they did replace some drive-line parts.



Yes it has reduced the degree of vibration. Also towing has reduced the vibration, in fact for a bit after the trailer is off the vibration is very little; but it comes back. The degree of vibration also changes with tire pressure; it worse at 45 psi (original dealer pressure) much less at 70 psi. The manual lever for the 4-wheel drive still vibrates when the rest of the truck is not bad you can still see/feel it in the lever.



Note: My car trailer is super light ~1000 lbs (it still killed my prior truck), and present mileage is still under 2000 miles.



I was able to get my friend to test drive the truck. He has a 1st generation truck and he now works at an RV shop.



He said two items; the one that leads to this post is tires, which I have not read too much about here.



Tires: I have BF Goodrich Rugged Trail T/A LT265/70R17



He said that a customer with a Ford had come in and thought a bearing was gone. After checking and reviewing the truck they determined it was the tires. He said what my truck feels and sounds just like the Ford. It just happened that the tires are the same as I have. He also said that a tire problem would be amplified in the drive-line. These tire have an aggressive tread block, and that these items combined may be setting up the harmonic.



Lastly yes it could be drive-line angles and I’m going to try putting weight in the bed and seeing what happens.



But my question to the fine people who read this is:

Do you have the vibration?

What tires do you have?

What type of load is in/on truck?



Lastly to those that did have the problem, has it gone away with more miles on the truck.



I do not want to lemon law out this truck. I like it too much.



Thanks

 

[raychem]

TO'Brien,



You are not the only one with this problem as others have posted and that I am also experiencing. I will watch this post closely to see if it sheds some extra light on the problem. Mine occurs and various speeds thought and they have already replaced the tail shaft section on my transmission(48re). So that you know, my vibration occurs at about 50 mph then disappears and returns at any speed over 85. I believe Pcline has been able to solve this problem as seen in this previous tread: http://turbodieselregister.com/foru...&perpage=15&highlight=vibration&pagenumber=5. I have read it several time but since i have never dealt with a drive line problem other than a bent drive shaft tube, the talk of all the angles is a bit confusing. Hopefully he will se this tread and chime in. I agree with you too, I love my truck to much to lemon law it.



Richard

 

[Kilby]

I have a harmonic vibe at 70 mph. It's pretty annoying since most LA traffic runs at 70. The vibe is bad enough that you can't recognize anything in the rear view mirror. Anything above or below 70 mph doesn't give the vibe. No, I haven't taken to the dealer yet.

 

[Barry]

My problem is with the A/C compressor. As you are running down the road, when the A/C comp. cycles in their is a roar that drowns out what little sound the engine makes and a vibration(buzz) that is transmitted thru the "go pedal" into my right foot. If this is "normal", I ain't lik'n it. Truck only has 500 miles on it but I don't see this getting any better. It is an 03. ( need to change sig. )

 

[Summit]

i have 15,000 mi on mine and it only gets much worse!! its worse @2100rpm but also does it @1600. its definatly harmonics and after you drive 100miles or more mine gets much worse, about 3X worse every time the A/C cycles youd swear it wont last another hundred miles without whatever it is letting go but it doesn't . well i have to go now. (off to therapy to see if the doctor can restore feeling in my hands)

 

[raychem]

Hey Barry and Summit, I also feel the AC comp kick in and out on mine, but it really does not bother me or it could also be that mine does not do it as hard as your's when they kick in. Just an idea though, with these 03 being quiet and the reduced vibration and harmonics, I think that we notice more of what has always been there, just more distinguishable now. Just a thought.



Richard

 

[Boonieman]

I have the A/C vibration also, and I think it's excessive. I also have the other harmonic type of vibration. Mine occurs at about 65 MPH, which is around 2000 RPM on my truck. I had been thinking that it was something in the driveline, however, if I put the tranmission in neutral (6 sp) and let it coast at that speed the vibration completely quits. Or, if I just push in the clutch at those speeds it also quits. Therefore, I've pretty much eliminated in my mind and problem with axles or driveshafts. I'm now thinking that it's an RPM relate balance issue, such as a flywheel or pressure plate issue. I'll have to go back and look at some of the other posts and see if any of the auto folks are having this same vibration... which would tend to steer my thinking away from a pressure plate issue.

 

[Vaughn MacKenzie]

Cummins Turbodiesel Harmonics

I have thought about this quite a bit, and I'm pretty sure the vibrations are natural first-order harmonics of a Cummins 5. 9L straight-6 turbo diesel. You have a high-compression engine, long crankshaft, very heavy pistons & rods, and 3 firing pulses per revolution. At about 2000rpm it appears these factors come together to create a resonance which is felt as a vibration. Doesn't matter if the engine is perfectly balanced or not. Many things in life have a natural "frequency" that they vibrate at. The glass you tap rings out a certain note. A bell has its own specific note. The frame on your truck will vibrate at a certain rate if you whack it with a rubber mallet. Your Cummins diesel engine has its own natural frequency as well, which seems to hit around 2000rpm.



To add to the vibration, I think the new stiffer frame helps transmit the vibes throughout the truck and especially up the steering column.



The fix? Maybe a different harmonic balancer, softer/redesigned engine mounts, or a balance shaft. I think chasing extraneous issues like tires, driveshaft angle, etc. won't help solve the problem much.



I have driven 6-7 different 03s and they all have the harmonic vibration. Some considerably worse than others.



Vaughn

 

[Prairie Dog]

Vaughn, you'll have to drive mine someday because I don't feel any vibration at all at 2000 RPM. Especially not through the steering wheel. Is it more of a buzz or does it shake the mirrors? How does it manifest itself?

 

[Steve M]

Vaughn,

I have to agree with you. All four of my Cummins powered Dodges have had this vibration. There's a slight harmonic vibration at 1400rpm and a more pronounced harmonic vibration at 2100rpm. I've found a new vibration that comes on around 2600rpm that the mechanic said was a trade off for quiet. He said I could unplug something to smooth it out some but it would be noisy like the last truck. I haven't stopped back by to ask him what it is I can unplug... It's definately engine. I can rev it to 2600rpm in park and it does the same vibration.

What I did have before the dealership changed the driveshaft with another truck was a slight driveshaft vibration from 45mph and up. It was a pulsating vibration that was there even with the trans in neutral and the motor at idle coasting from 70mph down.

So now that my drive shaft is almost perfectly balanced and I know the engine has some "normal" vibration to it (very mild compared to my Harley) it doesn't bother me when I feel it. Perception is the biggest part of the vibration problem. Once you feel it, you can't ingnore it until you know if it's normal or if something is wrong.

 

[TO'Brien]

I did a bad thing with both the service writer from the dealer and my friend. I press the overdrive button at 72 mph. The engine goes to readline. But the vibration/harmonic keeps going just the same. Also the vibration/harmonic is not present at other times when the engine is turn at 2000 rpm.



My way of now avoiding the issue is to drive at 76 mph which is ok till I hit traffic or I just stay below 68 (not).



I have found an interesting tsb

http://dodgeram.info/tsb/1998/18-49-98.htm yes it deals with 96-99 1500 but it has a good deal of info.



I'm in upstate New York. ?A/C? well yes the truck has it. It used to defrost the front window right? Oh ok I have tried it twice to insure it works but that was it. It does come on "Hard" the first time.



tim

 

[bighammer]

Mine has the AC vibration at about 70 mph. It sort of scared me on the way to Muncie. (first time it happened) I was in a construction zone and got warm, so I put on the AC. When I got out of the construction and sped up, I felt the vibration in the go pedal. Seems like you can hear it to. I drove for a bit and got cooler so I switched off the AC and it went away.



Even without AC there is a slight (very slight) vibration at around 70mph. It really gets worse with the AC on.

 

[CATCRACKER]

my vibration has gotten much less now with 8000 miles on it. i think it is the motor and the stiffer frame transmitting back through. however when i sit in my driveway and rev to 2200 i dont feel it all i can say is get used to it. put some 315's on it 70mph is around 1900 so i dont get the viration which starts at about 2000 rpms

 

[Steve M]

Stopped by the Dodge shop this morning. The mechanic said unplugging the rail pressure sensor would bring back the noise but it would also cause a trouble code and wouldn't run right. I think I'll skip playing around with it. Now that I know the 2100rpm and 2600rpm vibration are normal it doesn't bother me. We took the 5th wheel out last weekend and barely noticed the vibration. I must be getting used to the vibration without the noise blending in with it.

 

[Briman]

I have 12K on my truck. I have a vibration at 72-74 mph (2100 rpm). I have taken out my front drive shaft on more than one occasion and the vibration flat goes away. The dealer put in a front drive shaft from another new truck and the vibration went away for about 500 miles. After that the vibration came back and keeps getting worse. I think that the big fat double cardan joint in the front drive shaft is the problem, along with the long stub shaft on the passenger side of the front axle. The two of them together combine to create this vibration



I agree with Vaughn that the new trucks have more harmonic vibration from the engine and frame that the second gens did not have. This is not related to my vibration, although I do not care for this either.



I sure wish I had '00 truck back.



I think these new trucks are cheap pieces of crap. Fairly poorly designed in many ways. I have owned 7 Cummins powered Dodges since '94 and this one is the worst (except maybe the '96). The '94 had no problems at all and it was a first year truck. It is unfortunate and makes me think what brand to buy next time.



I would not hesitate one bit to turn this truck back under a lemon law.

 

[DIESELMAN]

:{ :{ :{ :{ :{ :{ :{ :{



Briman - If you are ready to part out your truck I could use some spare parts cheap, I'll trade you a '94 straight across,, deal??

 

[Turbo_Bob]

My harmonic vibration at 2200 RPM's & 72 MPH became more noticeable when I installed the muffler eliminator pipe.

It is just a straight six cylinder engine, thats all.

 

[Steve M]

Briman,

I have to agree with you to an extent... My '95 auto/3. 54 was a good truck but under powered. It had two problems in three years. The driveshaft had a bad vibration at 70mph and was replaced under a TSB. And the fuel shutoff solenoid burned out one day. My '98 5spd/4. 10 had a loose baffle in the muffler causing some electric transformer type noises and the fan clutch was defective making it's own noise through the fan. My '01. 5 auto/3. 54 was literally perfect. The 47RE shifted like it was in permenant tow mode and the motor produced enough power bone stock to rip the tires loose on dry pavement and towed our 10,400 lb 5th wheel 70mph in rolling hills with no sweat. It didn't have the first unusual vibration or noise and was pretty quiet on the road for a truck that had to be shut off at the drive up window at Wendy's. A month ago I would have taken it back in a second if I had the opportunity. I'm starting to like this truck and the quiet motor. The rear doors on the "perfect sized crew cab" are great as are some other things I like better than the '01. With almost 10k on the odometer, I'm getting used to the vibration and with no lift pump/injection pump worries, I'm not sure I'd want to go back. It's definately different. GM's are too pricey and only blind Ford loyalists are buying the 6. 0 right now.

 

[Briman]

Yesterday was not a good one, perhaps some of that was passed on in my post. The new truck is not that bad - just not that good either.....

 

[PCline]

Briman - if you're having problems with vibrations on your front driveline that go away when you remove it then it's one of two things, driveline balance or driveline angle.



Since you've had a second driveline that went "bad" after a few miles I'm guessing it's angle. The forward portion of the front diveling has to line up exactly with the front differential pinion angle. In other words, a line through the centerline of the front pinion should also continue through the centerline of the driveshaft.



In my opinion and experience, dealers are not knowledgeable enough to deal with driveline angles. Go to the best 4X4 shop around and have them check the angles.



If angles are your problem it's an easy fix. You simply tweak the front axle caster one way or the other to get everything lined up. Hopefully you're on the right side of the caster tolerance so that when you make an adjustment to fix the driveline angle your handling qualities don't go bad. Sag2 has accomplished this on at least one truck and I did it to mine also.



Good luck