Cyclical Vibration

[JohnnyR]

I have a 2005 Duramax/Allison and just recently noticed a vibration when idling in park that one can feel thru the floorboard. Cycle of the vibration is about 3 seconds apart and it goes away when you put the transmission in gear. I'm thinking it's perhaps the torque converter. I actually noticed on my son'd 2004 1/2 Duramax/Allison, then noticed it on mine although his seems to be more pronounced than mine. Has anyone experienced this before?

[Spartus]

Normal. My '03 does it. Did you watch the video that comes with the truck? They talk about all the neat noises the Duramax/Allison combo are known for.

[More Power]

Most Duramax trucks I've been around idled a little less smooth while cold than when it was warmed up. Plus, the "less smooth" idle could sometimes produce a light cyclic vibration.

Some of this could be due to variations in fuel rail pressure due to slightly a restricted fuel filter, or excessive pressure or vacuum in the tank, or due to the fuel control system attempting to compensate for viscosity variations in the fuel while cold.

Checking fuel rail "commanded" and "actual" pressures could help illuminate some of these possibilities.

When warm, the engine should idle pretty smoothly, but GM only considers an RPM variation in excess of +/- 100 rpm to be actionable.

Jim

[JD Diesel]

What video. ;) I did'nt get one tongue.gif

[redrider#1]

I have also noticed this vibration even when my truck is totally warmed up. If Johnny R is feeling the same thing I am, it is a very, very light change in the feel/vibration the engine/tranny are putting out at idle and only if you really listen and feel closely. Nothing to worry about, IMHO, but still just barely noticable.

[MikeC]

Video?? I didn't get no stinkin video!

Only thing I got was a payment book! :(

Mike

[silverback]

I paid cash and didn't get the video!!! I did get the vibrations though. As a newbie I thought something needed adjustment. After 2 years of buzzing I did get the dealer to tighten up my dashboard bezzle last week. It kind of moved the buzz around. Now I know it's a diesel thing. Our New Beetle TDI does similar things.
Enjoy,
KL

[JohnnyR]

I'm not describibg the typical buzz vibration one gets thru the brake sitting at a traffic light. I experience that on my previous two Duramaxes and my Cummins. This vibration is only as the vehicle is idling with the tranny in Park. It's not a steady vibration but can be felt as a series of 3 light taps in succession, then repeats itself 3 to 4 seconds later. Put the tranny in drive, and you don't feel it at all.
Anybody think it might be an engine or transmission mount loose?