2006 CM870 vibration in floor 6th gear

[berrytrucking94]

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?

[Shotgun74]

Possibly your clutch.

[the missing link]

When your going down the road like that , put you clutch in part way or just feel the pedal . That should give you some idea . Possible motor mounts ... They should be in lower gears at a harder pulls . Just my very limited knowledge

[snailexpress]

Could be many things.
You said vibration is only on one gear so it related to road speed.
Drive line, suspension front and rear, U-joints, bearing, differentials angle, suspension height and input shaft bearing. Anything or everything little bit.
Fuel starving is possible too.
Dyno is easiest, safest and cheapest way to find what is wrong

[hhow55]

I suggest checking the motor mounts.

[Pete379]

Is it a steady vibration or does it pulsate. The reason I ask is that I’ve noticed all sorts of issues over the years both vibrations and grinding that could be attributed to ride height on peterbilts with air suspension. I had an 07 that would vibrate in the cab under load and only in high range it turned out to be running too high I had to adjust the ride height valve. It’s worth a shot to take a look...

[the missing link]

Normally not all the time but when you are coasting ,stick it in neutral and feel the stick . The ujoint vibration will come though the stick .

[berrytrucking94]

(02-13-2018 )Pete379 Wrote:  Is it a steady vibration or does it pulsate. The reason I ask is that I’ve noticed all sorts of issues over the years both vibrations and grinding that could be attributed to ride height on peterbilts with air suspension. I had an 07 that would vibrate in the cab under load and only in high range it turned out to be running too high I had to adjust the ride height valve. It’s worth a shot to take a look...

It’s a pulsating vibration in the floor. If I rest my foot against the clutch while the truck is vabrating I can feel it very strongly on the clutch pedal so I’m thinking clutch related? Clutch has needed to be adjusted for a couple weeks now but didn’t seem that out of whack. I have yet to pop the inspection plate off to check everything out in there though

[the missing link]

It could be that the pressure plate lost a spring , throwing it out of Balance .
It's pretty common . I have yet to wear or heard of a clutch being wore out , usually the pressure plate starts losing springs or get weak .