2006 CM870 vibration in floor 6th gear

[Chamberpains]

With the new tid bit of information, it pulsates in 6th gear, I'm gonna recommend a thorough check of the rearends and drive tires. Either a dyno or get it up off the ground and drive it. Listen for a rearend grinding or look for flatspotted or out of round tires. Including the trailer tires. I just caught a set of my trailer tires that were slightly flat spotted sending a vibration up to the truck around around 30-50 mph. Also I rescently lost a rearend that made vibrations at the same speeds.

EDIT** I just went and re-read everything again. This complaint strongly points to rear engine mount bushings as others suggested. You won't always be able to see them worn out. Sometimes the rubber gets soft or the bolts wear in to the bushing and allows alot of movement with out looking shreaded or overly compressed.
Also you said

2007 Pete with an 06 cm870. Truck has just over 423k on it. Valves adjusted a few months ago, driveshaft/u joints are all solid..

I'm thinking if the truck, not the engine, is that old and only has that many miles on it. Then the engine mount bushing may have dry rotted. Trucks that old with that little of mileage usually sit around a long time not moving. That leads to a lot of dry rotted rubber components.

Read on if you wanna see how I search for any kind of vibration
END EDIT**

The speed of a vibration or pulse will often give away whats causing it. If its fast, then it has to be something that spins fast or can happen often. Drive shaft, tranny, clutch, engine, really messed up tire...

If it's slower, then it points to something that spins slower. Rear gears and bearings and flat spotted, mis mounted or out of round tires.

Why would it only happen at a certain speed? 2 things, either it stops occuring above and below those speeds or that because vibration travels in waves exactly like sound travels. You can't hear really low sounds and you can't hear really high sounds. That same principal applies to feeling a vibration in a vehicle. You can't feel it when its too slow most of the time because it's not happening or it doesn't have enough force to travel up to where you are or it's frequency is not often enough to be recognized. And if its too fast then its either corrected itself (often times rear ends correct themselves)or its vibrating fast enough that it can't be felt cause the frequency is too fast for the components around it to carry the vibration.

If you know what components with a flaw in it can make the vibration in sync. or in time with when you feel it that will also narrow most searches down quickly. Like a flat spotted tire will be once every rotation or once every couple seconds. Or a u-joint will be very rapid and get faster as the truck goes faster.

One last thing I do to narrow down a search while driving at speed is, if you can feel it with your hands in the steering wheel, then its in the steering system. If you can feel it in your butt(or the seat) than its drive line(drive shafts on back to the tires, including the trailer tires) if you feel it in the peddles its usually engine clutch or transmission.

[berrytrucking94]

I looked the truck up and down Monday/Tuesday before heading out to work(haul gravel locally)..

-Engine mounts were all tight
-driveline was solid from front to back
- all rear tires less than 20k on them and wear evenly

I try to stay on top of maintenance daily/weekly so these are things I usually keep an eye on anyways.


The vibration is only in the floor, even stronger through the clutch pedal.

Yesterday morning I started feeling it in all of the high range gears, some more than others. Finally took it to the local shop I’ve always used. They called me today and was told it needs a clutch, throw out bearing and input shaft...I hope they’re right seeing as it’s a $4-5k job. Shop hasn’t steered me wrong before so we’ll see :-/

[bossboy2]

(02-12-2018 )berrytrucking94 Wrote:  Currently having a vibration in the floor that continues to get worse. Only happens when throttle is engaged, under load up until 1600rpm then seems to even out. Mostly happens in the high side of 6th gear, some on the low side but not as bad (18 speed). As time goes on I’m noticing it very slightly in 7/8th around the same rpm.

Recently replaced the yoke and nut at the tranny because the big nut loosened up and was causing some vibration in the driveline.

2007 Pete with an 06 cm870. Truck has just over 423k on it. Valves adjusted a few months ago, driveshaft/u joints are all solid..

Any ideas what it could be? Vibration damper? Bearing in the tranny?

berrytrucking94, believe it or not I had this same problem in my Cascadia (2013) but my issue was in 8th gear. Yesterday I had all four drive shocks replaced and the problem is all but gone. There is a bit of vibration but that's pretty normal to me. I had the drive line checked out, torque arms replaced, new cab shocks, new front shocks installed and nothing. I was assuming it was just that good old freight "shaker" syndrome. I was shocked when I picked up my load today and the issue was gone. When is the last time yours were replaced?

[Hammerhead]

(02-16-2018 )berrytrucking94 Wrote:  I looked the truck up and down Monday/Tuesday before heading out to work(haul gravel locally)..

-Engine mounts were all tight
-driveline was solid from front to back
- all rear tires less than 20k on them and wear evenly

I try to stay on top of maintenance daily/weekly so these are things I usually keep an eye on anyways.


The vibration is only in the floor, even stronger through the clutch pedal.

Yesterday morning I started feeling it in all of the high range gears, some more than others. Finally took it to the local shop I’ve always used. They called me today and was told it needs a clutch, throw out bearing and input shaft...I hope they’re right seeing as it’s a $4-5k job. Shop hasn’t steered me wrong before so we’ll see :-/

DO NOT DO A CLUTCH JOB AND NOT CHANGE THE REAR MOTOR MOUNTS!!!
They're right there, so do it. At >400k miles they are done. They may not be toast, but their best service life has been used.

   
I would also do the rear main seal. It is the very next step after removing the flywheel to resurface it. You wouldn't wanna have to redo this job in a year to change that seal now would ya? The seal is marked in the photo...why wouldn't you change it when you can? The seal is only about $100.
Those are the things that IMHO {in my humble opinion} should be part of a clutch job without question.

I would strongly consider replacing the flywheel housing gasket while you're in there as well. This is going a little bit further and not a must IMHO, but certainly a consideration. Disturbing the back end of an engine of that age, even with low mileage, may cause this to start leaking in the next year or so...
If you're paying someone to do the work for you, as much as this adds to the bill, it removes the possibility of a repeat bill in the not to distant future because you tried to save maybe a grand...

[berrytrucking94]

Got the truck back Today:

-New clutch (I saw the old one and it was wearing very uneven.)
-flywheel resurfaced and housing gasket replaced
-input shaft and pilot bearing replaced
-rear main seal done

Tmrw it’ll be back pulling weight which will be the real test but bobtailing home ~30 miles felt like a whole new Truck. No vibration at all

Thanks guys for the advice and recommendations of things to look at