Strange Whistle From LLY? [Archive] - Diesel Place : Chevrolet and GMC Diesel Truck Forums

: Strange Whistle From LLY?


Brossjd
03-04-2005, 08:24 PM
:help:
Hello,
I just registered to this forum tonight. I am a recent Cummins reform. I purchased a new '05 GMC 2500HD last week. The new truck has the LLY and Allison auto. The truck is also 4X4.

My question is about a strange fluttering whistle sound from the turbo area. The engine is making a reasonably annoying sound when running at light load. The noise is definitely not the usual turbo sign. The best way to describe the sound is it sounds like a squeaky heater blower motor in an old muscle car. The engine makes the sound at about 10% to 25% load. The noise stops when truck is shifting gears under acceleration, or when I lift off the go pedal. I don't think the noise goes away under heavy load, but the engine and turbo noise drown it out. Censored
My dealer took the truck for a drive, but the mechanic could not get it through his thick head that the noise was most apparent under light load. He just kept flogging truck off every light, and even red lined it up the merge rap. He finally acknowledged hearing it when we got slowed down behind some traffic. He said he didn't think he could make it go away. However, He did not say it was normal!

If anyone has any information about this, I would very grateful.

Thank you

briano
03-04-2005, 09:23 PM
does this quite possibly resemble a drone? if so check this thread out http://dieselplace.com/forum/showthread.php?t=24776

something else...
the turbo will make different sounds depending on if its cold or warm because the turbo has variable vains on it that adjust to protect the turbo.

good luck with the trouble shooting

Oilbrnr
03-04-2005, 09:32 PM
Ex ISB owner here too. I *think* it is noise caused by EGR. Do a search here, and disconnect the EGR and see if it (the noise) doesn't go away.

It has been a few months since I disconnected mine (put it back) but as I remember the noise went away. Also sounds like playing cards on the spokes of a bike?