Up and Down Vibration at Speed

[noteven]

It is important to set ride height as per factory specs for  correct driveline angle. Kenworth adjusts engine tilt to accommodate wheelbase so if your wheelbase was altered you could be out a degree or two which is setting up a flutter... 

But - the driveline turns at many rpm and a is normally a vibration at highway speed if something is amiss.

If the vibration is a certain frequency, try to think of what on the truck turns at that frequency. Is it tire rpm, axle rpm, driveline rpm, trans input/clutch/engine rpm? 

Is it present all the time, under power only, coasting, decelerating, same with retarder on or off? 

Then start there and change one thing at a time.

But I’m kind of in the rear wheels camp too from what you are writing ... 

Do you have Centramatic balancers? 

[Steve from SoCal]

Unless the rear axle is from an old truck the hubs should be hub-centric, you can see 5 nub at the base of the wheel studs.     

Steve

[porky69]

If you find the right shop they may have access to some high tech vibration diagnostic equipment.

 

Years ago the company i worked for had a bed truck (similar to https://www.camex.com/trucks/bed-pole-rig-up-trucks/equipment/11872/2015-kenworth-c500-bed-truck/) that had a vibration that no one could diagnose. Threw lots of parts at it with no results (on warranty luckily). Dealer ended up accessing a system where they puts sensors all over the truck (various points on frame, multiple points on each axle, engine, transmissions,etc) and was finally able to determine where the vibration was. If I remember correctly it ended up being a rear suspension issue (100,000lb capacity rubber block) 

[Chad Heiser]

2 hours ago, noteven said:

It is important to set ride height as per factory specs for  correct driveline angle. Kenworth adjusts engine tilt to accommodate wheelbase so if your wheelbase was altered you could be out a degree or two which is setting up a flutter... 

But - the driveline turns at many rpm and a is normally a vibration at highway speed if something is amiss.

If the vibration is a certain frequency, try to think of what on the truck turns at that frequency. Is it tire rpm, axle rpm, driveline rpm, trans input/clutch/engine rpm? 

Is it present all the time, under power only, coasting, decelerating, same with retarder on or off? 

Then start there and change one thing at a time.

But I’m kind of in the rear wheels camp too from what you are writing ... 

Do you have Centramatic balancers? 

The vibration is there under power as well as when coasting (take foot off accelerator) as long as I am traveling at the correct speed.  I will have to test deceleration.  It is a short speed window where the vibration occurs, so I haven't really paid attention what is happening on deceleration.  When decelerating, it doesn't take long to get outside the speed window for the vibration to stop (if that makes sense), so I don't really remember if the vibration continues as I decelerate.

I do not have centrimatics or any type of balancers n(other than wheel weights on the wheels), but I am considering adding them to see what happens (although I would rather cure the problem rather than mask it).

My problem is most of my trips with the truck are local and on winding roads.  This doesn't allow me to get up to the 60 mph window very often.  Even when I do, it isn't for very long (the joys of still working and being mostly a weekend traveler right now along with living in a rural county that has no interstates or straight highways).  This is another reason this vibration has been a low priority issue for me because I don't encounter it regularly. 

My trip to Las Vegas earlier this month was the first time in a year I really spent any sustained hours on an interstate at the right speed to get the vibration.  This brought it back up to my immediate attention.  That combined with the fact the last two years of services have just been regular maintenance stuff with no actual repairs needed (so I haven't spent a lot of money on the truck recently) has got me to a place that I am ready to solve this problem (even if it takes throwing a few bucks at it ).

[Showme]

Looking over your profile, I did not see info about your truck specs, so just a quick quess. If the real axle has been changed and was misaligned with the front axle, check pinion angle to drive shaft. Spicerparts.com has a driveline angle calculator on there website. Google, driveline angle for instructions on checking driveline angles. Digital angle levels are available from Lowe's or Home Depot. Donot have enough space available for complete how to instructions on driveline angles but it is all available  online. 

All driveshaft will have some bend or wave within manufacture spec, so sometimes taking the driveshaft loose at the rear axle and turning 180 degree will help a vibration. 

[Chad Heiser]

1 hour ago, Steve from SoCal said:

Unless the rear axle is from an old truck the hubs should be hub-centric, you can see 5 nub at the base of the wheel studs.     

Steve

I had Lug-centric and Hub-centric reversed in my head when I said my wheels where lug-centric earlier.  They are in fact hub-centric. 

You have got me thinking though.  I can't remember when I first really noticed the vibration in the truck, but it was relatively early in my ownership of it (again it was minor and a low priority item on my list of wants and needs for the truck at that time).  Now I don't remember if it was there before I replaced the tires or not.  When I replaced the tires, I also replaced the inside dual wheels on both sides.  They were old steel wheels and were pretty rusted and chewed up.  The tire shop just grabbed some new steel wheels they had in stock and mounted them up.  I would think they would be smart enough to not give me the wrong style wheel, but I have never actually looked at the steel wheels to see what type they are.  The only time they have ever been off the truck since they were installed was last fall when I had the rear wheels balanced at Speedco in Corning, CA.  Again, I would hope that they would notice if they were the wrong type of wheel, but who knows.  It was a quick in an out for a simple balance.  How much did they pay attention to the inside wheels????  I need to check this just to be sure now.

[HERO Maker]

Chad, if you get a chance, chock your front tires and lift the rear up to spin the tires.  Put anything on the ground next to the tire while spinning and see if the roundness of your tire  is true.  You'd be surprised.

[Chad Heiser]

I haven’t had time to put any effort into troubleshooting this issue yet.  I did, however, order a set of centramatic wheel balancers today.  They are having a “show” special (I didn’t ask, but I am assuming it is a MATS special).   I got them for $179 a pair with free shipping.  That was about a $60 total savings for the two pairs I ordered not including shipping.  I guess I picked the right time to call centramatic.

[TXiceman]

Chad,I tried the Centramatic balancers on my F350 dually and the vibration was worse.  Finally sent them back for a refund.

Ken

[Randyretired]

I put Centramatic balancers on my truck and I like them.  Before I put them on the truck would vibrate and shimmy a little.  After it was just as bad.  Found a bad front tire.  It is smooth now.  These won't fix a serious problem but seem to work to keep things in balance.

[Dollytrolley]

On 3/14/2018 at 6:33 PM, Chad Heiser said:

  When traveling around 60 mph, the truck starts to vibrate up and down slightly.  It is almost like it is driving over a washboard road.  The steering wheel is dead straight with no warble or movement and nothing is going side to side, it is all up and down movement.  It isn't horrible, but it is irritating.  At lower and higher speeds, it is not there (at least I don't notice it until about 60 MPH).

Good morning Chad,

Its a bit tough doing vibration sleuthing by remote text however..........let me throw my two cents into the game......

Of the course of a lifetime of dealing with marginal machines that have been trying to kill me I have become "involved' with shake-rattle-and-roll equipment and as such have become involved taming some of these bad-machines........

A couple of life long geezer friends have been involved in the vib-game all of their lives and some of their equipment is so old it has vacuum tubes but still solves major problems..........now don't get me wrong they are not stuck in the dark ages and some of their equipment is latest wiz-bang-laser-wireless-do-dads so things get fixed pretty darn quick once the geezer gets at the offending machine.

I still have a bit of vib-test equipment laying around but I seldom do much work anymore but IF you run out of options perhaps I could get a few plots that might suggest the source of your problem(s).

In the vibration-game most folks tend to want to point the finger at UN-Balance......but......many, many times other factors are the root cause of vibrations..........

Your description of the "vibration" becoming intense in a rather narrow speed range tends to support a root-cause of looseness and or alignment.......

It sounds like you have a nice shop that works on your truck and this is good, however often "little-things" can be overlooked that can cause good shops to bang their head against the wall.

Here is my shot in the dark..........IF ........IF the driveline is "suspect" what does the slip-joint look like? Is it tight? Is it straight? Are the splines worn? Are the splines straight? 

Now here is the "BIGGIE" ......IS the driveline "IN-PHASE" (Are the u-joints in radial-phase relation to each other within KW specs?).

Chad you would be AMAZED how many drivelines are running out-of-phase........

How can a driveline become out-of-phase?

Simple......most slip-joint have SIXTEEN splines and if the slip-joint is taken apart and then reassembled with the splines NOT in the original CORRECT position you WILL have a OUT-OF-PHASE driveline.......

This is so simple that it is OFTEN overlooked.

With vibration test equipment out-of-phase driveline is so simple to detect because the frequency of a out-of-phase driveline is TWO TIMES ROTATIONAL SPEED of the actual driveline.

What you feel mostly in the seat of your pants is the AMPLITUDE (you say "up and down") movement but FREQUENCY (How often amplitude occurs) is much harder for humans to judge.

Vibration test plots show both Amplitude and Frequency so it tends to give informed info to determine the root-cause of the problem.

If this this problem persists .........perhaps I might escape out of central Oregon stable-cleaning chores for a day and come over to the Idaho rally for a few hours to run a few vib-plots on your rig and really add to the head scratching..........

If you what to chat try my cell at (520) 891-3695 ..........cell coverage is a bit sketchy at our camp but most days it works.....sorta...

 

Drive on.............(Shake-Rattle-and no-roll......) 

[noteven]

Chad we got so busy talking motor bikes, solar, and the quality of the beer we totally forgot this issue .

Like Dolly says step one is “what kinda vibe is it?” 

[HERO Maker]

Chad, just saw this again.  As mentioned, Centramatics won't fix out-of-round tires.  What I described would be a very no expense test to see if you have a tire problem.

I was amazed after having my tires trued.  Just a starting point.

[Chad Heiser]

13 hours ago, Dollytrolley said:

Good morning Chad,

Its a bit tough doing vibration sleuthing by remote text however..........let me throw my two cents into the game......

Of the course of a lifetime of dealing with marginal machines that have been trying to kill me I have become "involved' with shake-rattle-and-roll equipment and as such have become involved taming some of these bad-machines........

A couple of life long geezer friends have been involved in the vib-game all of their lives and some of their equipment is so old it has vacuum tubes but still solves major problems..........now don't get me wrong they are not stuck in the dark ages and some of their equipment is latest wiz-bang-laser-wireless-do-dads so things get fixed pretty darn quick once the geezer gets at the offending machine.

I still have a bit of vib-test equipment laying around but I seldom do much work anymore but IF you run out of options perhaps I could get a few plots that might suggest the source of your problem(s).

In the vibration-game most folks tend to want to point the finger at UN-Balance......but......many, many times other factors are the root cause of vibrations..........

Your description of the "vibration" becoming intense in a rather narrow speed range tends to support a root-cause of looseness and or alignment.......

It sounds like you have a nice shop that works on your truck and this is good, however often "little-things" can be overlooked that can cause good shops to bang their head against the wall.

Here is my shot in the dark..........IF ........IF the driveline is "suspect" what does the slip-joint look like? Is it tight? Is it straight? Are the splines worn? Are the splines straight? 

Now here is the "BIGGIE" ......IS the driveline "IN-PHASE" (Are the u-joints in radial-phase relation to each other within KW specs?).

Chad you would be AMAZED how many drivelines are running out-of-phase........

How can a driveline become out-of-phase?

Simple......most slip-joint have SIXTEEN splines and if the slip-joint is taken apart and then reassembled with the splines NOT in the original CORRECT position you WILL have a OUT-OF-PHASE driveline.......

This is so simple that it is OFTEN overlooked.

With vibration test equipment out-of-phase driveline is so simple to detect because the frequency of a out-of-phase driveline is TWO TIMES ROTATIONAL SPEED of the actual driveline.

What you feel mostly in the seat of your pants is the AMPLITUDE (you say "up and down") movement but FREQUENCY (How often amplitude occurs) is much harder for humans to judge.

Vibration test plots show both Amplitude and Frequency so it tends to give informed info to determine the root-cause of the problem.

If this this problem persists .........perhaps I might escape out of central Oregon stable-cleaning chores for a day and come over to the Idaho rally for a few hours to run a few vib-plots on your rig and really add to the head scratching..........

If you what to chat try my cell at (520) 891-3695 ..........cell coverage is a bit sketchy at our camp but most days it works.....sorta...

 

Drive on.............(Shake-Rattle-and no-roll......) 

Dolly, thanks for the offer.  I may take you up on that if the problem persists.  My driveline was pulled a while back to get balanced.  It is possible it was not put back in the proper phase.  The only caveat to this is the driveline was sent out to be balanced because of the vibration, so it already existed before it was pulled.  It is quite possible that when the truck was singled, the drive line was put back together out of phase and then pulled and put back together the same way when I had it balanced.

By the way, you should come on over to the WCR in June anyway.  You are so close it would be an easy long weekend trip for you.

13 hours ago, noteven said:

Chad we got so busy talking motor bikes, solar, and the quality of the beer we totally forgot this issue .

Like Dolly says step one is “what kinda vibe is it?” 

Your right, we should have talked about it.  It completely slipped my mind during our meet up.  The vibration is a slight up and down like driving on a washboarded gravel road.  It occurs at around 60 mph.  Faster or slower by a few mph and it goes away.

 

1 hour ago, HERO Maker said:

Chad, just saw this again.  As mentioned, Centramatics won't fix out-of-round tires.  What I described would be a very no expense test to see if you have a tire problem.

I was amazed after having my tires trued.  Just a starting point.

I know the centramatics won’t fix out of round, but I figure the centramatics won’t hurt anything and may help.  Besides, I’ve been looking at adding them for a while anyway and I figured why not start with something easy.  I have had my front tires trued, so I know they aren’t out of round.  I have only balanced the rears, so they could have an issue and are on my list to get done.

[Chad Heiser]

A little bit of an update for this topic.  I installed the Centramatic wheel balancers and they made a big improvement on my overall ride in the truck.  We went to Havasu for a week and the vibration was mostly gone.  On good highway, the balancers compensated for the vibration I was feeling previously and smoothed things out.  The vibration was completely gone.  I had forgotten just how smooth the ride could be in the truck.  On bad/rough sections of highway, the up and down vibration was still there, but wasn't quite as bad.  I think the additional bouncing due to the rough road made the balancers less effective.  My overall impression of the balancers is very positive and I am glad I bought them.  I am now leaning more toward my issue being a tire issue.  New tires aren't in the budget this year, but maybe next year I will replace them.  They will be six years old next year.  I was hoping to go seven years on this set, but I will push that up a year based on my experiences so far.

[jenandjon]

Last summer I spent a couple grand over a few months chasing a bad vibration in my pickup. So bad I was ready to trade it off. This is how we found it. I don't know why a truck would be any different. Just bigger. I was working with an old school mechanic on this. I would not have thought of it myself.

 

Put your drive axles up on jack stands and run it up to 60 mph. If the vibration is there then you have just ruled out the entire front end as a problem. If there is no vibration then you know it is in the front end. If the vibration is there then remove the drive wheels  put on a couple lug nuts back on to hold the drums on and do it again. If it persists you have just ruled out the tires as the problem and it is likely the drive line.

This is very important.....I did this twice. The first time I had my pickup on a lift. The lift must have absorbed the vibration We couldn't find anything wrong. Then I put it on jack stands on concrete. That amplified the vibration so bad I thought my mirrors were going to shake off. We found that the driveshaft was out of balance.

So, jack stands on concrete, block the front wheels and be careful.

 

 

[ARGO]

Desert miner mentioned U joints. Once upon a time, I bought a new Pete, had the same problem. Warranty paid for it, but after EXTENSIVE speculation/investigation, it turned out the U joints were 3 degrees out of phase in the d-shaft. 3 degrees doesn't sound like much, but could easily be missed when they were checking the dshaft for other things.

[HERO Maker]

15 hours ago, jenandjon said:

Last summer I spent a couple grand over a few months chasing a bad vibration in my pickup. So bad I was ready to trade it off. This is how we found it. I don't know why a truck would be any different. Just bigger. I was working with an old school mechanic on this. I would not have thought of it myself.

 

Put your drive axles up on jack stands and run it up to 60 mph. If the vibration is there then you have just ruled out the entire front end as a problem. If there is no vibration then you know it is in the front end. If the vibration is there then remove the drive wheels  put on a couple lug nuts back on to hold the drums on and do it again. If it persists you have just ruled out the tires as the problem and it is likely the drive line.

This is very important.....I did this twice. The first time I had my pickup on a lift. The lift must have absorbed the vibration We couldn't find anything wrong. Then I put it on jack stands on concrete. That amplified the vibration so bad I thought my mirrors were going to shake off. We found that the driveshaft was out of balance.

So, jack stands on concrete, block the front wheels and be careful.

 

 

I would think that "out of round" tires would not show up as vibration with the wheels in the air.  Not sure about that, or if the out tire would also be out of balance?

[jenandjon]

8 hours ago, HERO Maker said:

I would think that "out of round" tires would not show up as vibration with the wheels in the air.  Not sure about that, or if the out tire would also be out of balance?

With the axles on jack stands the vibration is amplified. There is no weight on the tires. No bumps compressing the suspension.