Engine Vibration at 1200 to 1500 RPM

[Macon Rounds]

I have a 2006 crew cab short bed Duramax truck.

While having truck in park or in neutral and accelerating through RPM range from idle to 5000 RPM truck has a distinct vibration from 1200 to 1500 RPM. Vibration is not evident at any other RPM.

This vibration is also evident while driving in any gear at any speed that falls within the 1200 to 1500 RPM.

I have been chasing this vibration issue since the truck had 100K and it now has 190K. I initially believed it was a driveline problem and I have change EVERY rotating part aft of the transmission including transfer case, drive shaft, rear differential and bearings and the front wheel bearings. With no improvement with that "particular" vibration.

I have an evolution programmer on the truck but have disconnected it and the problem still exists.


Truck runs and performs fantastic.

Anyone have a cure for this engine vibration between 1200 and 1500 RPM while truck is in park or neutral?

Thanks in advance

[JeepSJ]

Well, since it does it in park and neutral, that really eliminates anything behind the transmission or anywhere else in the chassis. You need to focus on everything in front of the torque converter.

- Balancer/damper (see the gas truck section for a picture of my balancer; it only had a vibration at certain RPM)
- Belt driven accessories
- Flexplate
- Torque converter.
- Fan clutch

[Macon Rounds]

Yes i agree !!!! About focusing on engine, however it could also be the flex plate or torque converter as
they both still rotate in park and neutral. And are my suspicion. However big labor expence just verifying there integrity.

Like i mentioned, i only INITIALLY thought the problem was driveline because it also vibrates while driving and i dont typically rev the engine thru the RPM range while in park.

Also many forum articles discuss and direct a person to frame beaming, front wheel bearing failure, transfer case issues and driveshaft vib. All of which i have addressed and have experianced minimum to GREAT improvement.

So here i am troubleshooting this issue down to the point of enging vibration from 1200 to 1500. And hoping one of you fellas would have experianced this and found a FIXED ! :)

[EdHale]

If memory serves there was a harmonic issue relating to the drive shaft on the 2006's. I have one and I never had the problem. Sorry I don't remember the details from that many years ago. I don't recall if it was with both the LLY and LBZ engines or just one of them since both were used in the 2006 models.

[a5150nut]

I have an 06 with LBZ at 66k mi I don't have any vibration problems. And hope I don't now that I have said this.

Sweetest truck I have ever owned.

[More Power]

I assume the engine is not setting any codes.

I would spend some time with a Tech II scan tool, looking at the various engine speed sensors, looking at injector balance, use it to disable one cylinder at a time, and anything else I could think of. Do these tests while running the engine in Park through the engine speed you notice the worst of the vibration.

There's a whole lotta rotating inertia with the engine running at 1200-1500 rpm. Something significant is happening if you can feel an objectionable vibration from the driver's seat. It should be measurable using a Tech II.

[Macon Rounds]

I am not familiar with that tool and I do not have ready access to a tech II tool. I know they are out there used or cheap clones on ebay but I understand they can cause more problems than they fix.
Ref: http://www.ebay.com/gds/GM-TECH-2-Diagnostic-tool-A-quick-word-before-buying-on-Ebay-/10000000178110787/g.html

I will however ask around and find a HP or OTC one as I understand they are reliable ....

Addition info on the my truck vibration:
No vibration when truck is cold. Driving or in park or neutral.
Vibration is SIMILAR to tire out of balance vibration. Low frequency.
Most noticeable in 4th 5th and 6th gear.

[More Power]

Just a thought.... If you are new to diesel engines, a typical and normal operation may be interpreted as a problem.

Due to how a diesel engine operates (compression ignition), considerable torque impulses can be found in the crankshaft/drivetrain at certain engine speeds and loads. Generally, the powertrain control systems minimize this to a point of being hard to feel, but they can still be felt.

Are you experiencing this while driving with the Tow/Haul mode activated and with the engine operating at a lower engine speed? Is there any change in the vibration with/without T/H engaged in the RPM range you mentioned?

Have you had an injector balance test performed?

Keep us posted. Jim