Annoying Vibration with 18 speed

[bulldogger]

Have a 2013 Mack pulling tandem gravel end dump that has a vibration that concerns me a little.

More noticeable under load and only happens in 11th and 12th between 1400 and 1800rpm.

Dealership has looked at it several times and seems to have no cure.

Dash is beginning to shake a little more now with extra miles and am wondering if anyone else has come across this.

Dealer now claims that this is normal for all Macks with Volvo engines and we should just accept it.

Anyone?

Thanks. First time poster.

Bull

[wheeler73]

Have they checked the ride height and driveline angle? Have seen this cause a lot of vibration issues at different rpms. Also have seen injectors cause vibration issues at different times.

[ws721]

Just went thru this with the leased milk trucks. They kept insisting it was clutch or tires. I kept bringing them back saying its driveline. The same symptons you are describing. @ months later the dealer finally says "the drive line was out by 2 in." Just something you may want to look into

[bulldogger]

Suspension and drivelines have been checked by dealer. They even re-balanced some driveshafts. Don't think they went into the injectors.

Driveline was 2" out where?

Weird thing is, we are looking at trading off a second used truck on another 2014 Mack that is in stock on dealer's lot. We test drove it, looking for same vibration and it was there even on the brand new unit.

So we thought maybe the dealer's claims of it being normal are true, except now we are re-thinking the purchase.

Not sure what our next step should be.

[gearhead204]

STEP TWO Knock a axle out of each rear end and run truck up to problem speed , then start looking for the problem.

STEP ONE Let me ask another question when this problem occurs if you push in on the clutch does the problem change rapidly? don't change throttle position just add and remove power with the clutch and see what happens. also are you sure it don't do this at lower speeds?

[bulldogger]

Thanks for all the responses guys.

Depress the clutch with no change in the throttle position and the vibration disappears.

To my knowledge they have not tried removing the axles.

[gearhead204]

I'd drop the drive shaft off the back of the trans and see what you get. if that is good then remove an axle shaft from each axle and run up to speed. sounds like a damaged rear end

[ws721]

The suspension height was 2 in to high. Wrong driveline angle was the culprit in the case of our 3 trucks

[bulldogger]

I'd drop the drive shaft off the back of the trans and see what you get. if that is good then remove an axle shaft from each axle and run up to speed. sounds like a damaged rear end

Dealer refuses to troubleshoot it anymore. Says all Macks are that way, just deal with it. Truck is still on warranty.

[bulldogger]

The suspension height was 2 in to high. Wrong driveline angle was the culprit in the case of our 3 trucks

Ride height was checked and different settings were tried with no improvement.

[mrsmackpaul]

things you need to check are

phase angle which is the relation ship between drive shafts assuming there is more than one drive shaft between between front diff and gear box when you look down the drive shaft the uni cross's between the two shafts should not be in a straight line the rear shaft should be one splined notch behind the front shaft in the oppiset direction of travel for the pto shaft other wise you will get torrsional vibration between the two shafts

the other thing to check is the vertical angle of all the uni crosses must be exactly the same other wise the unis accelerate deaccelerate at different speeds which will cause the same problem as described

both of these problems will not be picked up by balancing the drive shafts as the shafts are not out of balance but will cause the annoying vibration you mention and are both caused by lack of properly trained mechanics they just no that computer says do this and thats what they do so it must be right that is the modern world though

here is a link thingo for the second problem that describes it much better than me

http://www.hotrodhotline.com/md/html/drive_shaft_harmonics.php

will have to dig out picture of the first problem I spoke about had quick look on google only found the second and most common problem hope this is of some help

Paul

[wheeler73]

I like to set both rears up on jack stands and run the truck. I have found a lot of vibration and rear end issues this way.

[bbigrig]

Had the same problem with my heavy spec 2013 505 MP8. has Meritor 46's with 4-way lockers. They did shocks, ride height blah, blah blah.....I said seems only under load and at Higher speeds etc. I suspected combustion gas getting into fuel system when hot and under load like I use to see on 60 series Detroit's (basically same injector/cup setup).

Betcha every time you bring it to dealer you have a hard time proving that the "Vibration" is happening???? Mine turned out to feel like a vibration only to find out it was more of a studder. I was lucky 1 nightshift Tech agreed with me. Days would fluff me off like you.

It got worse and worse to the point where it would finally "vibrate" when the dealer had there hands on it. After all the wasted time on drive train turned out to be Injector cups and a fretted(cracked) injector tip pushing combustion gases into the fuel system. At 20,000kms they did 6 cups and all 6 injectors. No more "Vibration".

May not be the same issue as yours but mine took a while before they saw the bubbles in the fuel system sight glass test kit. Stick to your guns if you think this sounds familiar. If I hadn't I would have been like you. It took Mack almost a week to come up with the 6 injectors to change over because at the time they were replacing so many of them they had a hard time stocking them. I also adjusted my ride height back to where it was when it was delivered.(they lowered it to the point of almost covering the entire bag stool at ride height) It made no difference in my "Vibration"

Keep in mind...If its a cracked tip or combustion getting past the injector and cup they are more common to happen under load and hot. Is this issue the same when you are running empty? My issue had to be hot, under load, and at rpm's that demanded the most fuel and produced the highest in cylinder temps.

I see you mentioned when you depressed the clutch the vibration disappeared. This could also be you breaking the high torque load on the engine. Mine wouldn't vibrate unless it was under load. Bobtail it wouldn't produce this issue. Good luck!

[bulldogger]

Ours is a 2013 505 with the 46's as well with 36000kms on it now.

And yes, it only happens under load, You really can't notice it with an empty trailer.

Is there an easy way to test the injectors or do I have to convince them to do this in a leap of faith?

Thanks.

Bull

[bbigrig]

The Combustion gas getting into the fuel system got worse as the mileage creeped up. I noticed my issue within 10,000kms of delivery. Luckily I turn wrenches for a living and have lots of experience in the field with everything except my current MP power. I'm starting to see they have common issues like everything else on the road. It was tested after the engine was hot with the sight glass in line to the fuel system after a road test.

Its sad but the mechanic that agreed with me had diagnosed other similar units to the disbelief of the DSM when this problem started arising with my unit and others.

You need to find another Mack dealer to bring it to. If it was driveline related it would do it all the time at speeds that would put the drive train out of balance. Breaking the torque/load by depressing the clutch is a good sign that its not a constant like a diff or drive shaft balance. while in motion at what ever speed, a balance issue is usually no effected by load or torque. its usually speed(RPM) and balance related. Diff gear wear or play still could be an issue with torque or load being the factor that effects your issue from re appearing.

I'm still on the injector related problems. Keep on them till they come back proving that they tested the fuel system with the Volvo/Mack approved fuel system test tools. Not just some fuel return line into a bucket! lol.

[bbigrig]

Are you in Canada as well? I see you are using Km's in your description. I

[bulldogger]

Wpg., Manitoba.

[jnr_ate]

definitely driveline related?

I reckon engine flutter, we had a really bad run of injector tubes/orings on mp8s in Australia.

if you make it really lug, make it flutter/vibrate as much as possible, the loosen off your fuel filter.

if the fuel squirts out, its orings... combustion in fuel system. however, usually comes with hard starting.

[bbigrig]

The 2013 MP8 I own had cups and injectors done at 20,000kms approx. It only had the shuttering issue under heavy load and hot. That truck never produced the loss of prime or hard starting. I have had another of my MP8's do the shutter and hard starting. Seems you can get multiple characteristics for the same problem with MP series engines.

[slingblade]

one of the RDs where i work had a bad vibration,kept telling the owner about it,nothing got done till the rear yoke on the trans finally wiped the speed sensor out

thats when they found the nut holding it loose,tighted it up and the vibration under load and at speed went away,another older RD had a very bad vibration that we couldnt find till it finally broke the rear drive shaft universal between the diffs,replaced the yoke on rear diff and the joints and 98% of the vibration went away,mack should be ashamed of themselves turning out new trucks with the issues you talk about on here and no one knows what the problem is