800-1000 rpm vibration

[06SLTcs]

I just noticed this yesterday and not quite sure what to think about it. In park bumping the rpms to inbetween 800 and 1000 get a pretty good truck vibration. The engine doesn't seem to be running rougher but its hard to tell since its just above idle. Idles dead at 750 and normal as far as I can tell and after 1000 its non existant. I tried feeling it at speed around those rpms but between the road its hard to notice.



I'm thinking it may just be a resonate point but wanted to see if anyone else has noticed. Last oil report showed no fuel as of 3500mi ago and I adjusted the valves 18. 5k ago. Fuel milage has been consistant since it got warm down here.

 

[MChrist]

Mine is as smooth as a baby's butt. How many miles do you have now?

 

[thomasrmmr]

my 06 had it for around 5000 miles when it turned 75000 i took off n reinstalled harmonic balancer n vib went away ?? get that !

 

[Prairie Dog]

I don't know if this would affect it at that RPM but you may want to check you harmonic balancer for signs the rubber is failing and coming out.

 

[06SLTcs]

Bout to turn 119k on it. Got a new tank of fuel and it seemd to be better. Also cold it seems to be smoother than warmed up at those rpms. I'll get under and check the balancer. Other thought could be an injector or two on its way out. However it seems to be fine as far as I can tell everywhere else. Though no fuel in the oil. Unless its a recent thing. Haven't actually pulled the stick lately.

 

[thomasrmmr]

mine didnt viberate on the way up in revs only as it came down at 800 to 1000

 

[06SLTcs]

mine didnt viberate on the way up in revs only as it came down at 800 to 1000

Did you rotate it or just pull it off then right back on?

 

[Chemical03]

06SLTcs I am having the exact same issue did the vibration go away with the reinstall of the harmonic balancer? I had them check all the u joints/ball joints and tires everything was fine.

 

[thomasrmmr]

tookit off installed 1 hole off , it only made vibe on the way down so how could an injector make it vibe it was off throttle no vibe on the way up just as it swung past 1000 down to around 800 thats all gone ???

 

[Prairie Dog]

06SLTcs I am having the exact same issue did the vibration go away with the reinstall of the harmonic balancer? I had them check all the u joints/ball joints and tires everything was fine.

Did they take the drive shaft down and disassemble the joints? There's no way to just look under the truck and see a failing joint unless it has already started to come apart. Bad needle bearings will cause all kinds of problems long before a visual check will tell.

 

[06SLTcs]

tookit off installed 1 hole off , it only made vibe on the way down so how could an injector make it vibe it was off throttle no vibe on the way up just as it swung past 1000 down to around 800 thats all gone ???

?? I didn't really follow that other than you rotated it one hole.



I only notice on the way up under throttle. So thats why I think it *might* be an injector issue. Especially as of late as I have start up smoke even at 60F for about 30 secs. Little loop in the idle then it settles out. I haven't had time to mess with it lately unfortunantly. Going to perform a leakdown test first, then move on to the damper.

 

[cerberusiam]

tookit off installed 1 hole off , it only made vibe on the way down so how could an injector make it vibe it was off throttle no vibe on the way up just as it swung past 1000 down to around 800 thats all gone ???

I am still trying to figure out how you rotated it one hole when there is an alignment pin there? That no worky?

 

[Dieselnerd]

Mine was vibrating more than usual too. I checked the damper and the rubber looked good but the scribe marks on the damper were slightly off. You are supposed to inspect the damper every 30,000 miles according to the maintenance schedule.



I replaced my damper with a "Fluidampr". Much smoother now.