New Sierra: engine noise

Robber55 · June 1, 2006

I am totally new to owning a diesel and just got a Sierra Crew Cab to pull my toyhauler. Yesterday, I got to 500 miles with no issues and decided to take it onto the highway to see how it did at high speed. I noticed that at 64 to 67 miles per hour I could hear and, to some degree feel, what seems to be a very low pitched howl or rumble from the front. It mostly goes away at higher speed and is not noticeable lower. I then ran at lower speed and by using tow haul mode was able to get the same noise at the same RPM. Definitely tied to RPM, not speed. Is this normal? Turbo maybe? Truck seems to perform well with lots of power (understatement) and no noticeable smoke.

snoman · June 1, 2006

I am totally new to owning a diesel and just got a Sierra Crew Cab to pull my toyhauler. Yesterday, I got to 500 miles with no issues and decided to take it onto the highway to see how it did at high speed. I noticed that at 64 to 67 miles per hour I could hear and, to some degree feel, what seems to be a very low pitched howl or rumble from the front. It mostly goes away at higher speed and is not noticeable lower. I then ran at lower speed and by using tow haul mode was able to get the same noise at the same RPM. Definitely tied to RPM, not speed. Is this normal? Turbo maybe? Truck seems to perform well with lots of power (understatement) and no noticeable smoke.

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Curiuos, I know that GM changed the way that they balance the engine in late 2005 for 06 models. If it occurs regardless of throttle setting it tends to suggest a balancing issue but it if varies with power setting at stated RPM then it may be a injection timing issue. I would take it to a dealer and show them what it is doing (take them for a drive, just do not tell them about it.)

Robber55 · June 1, 2006

I am totally new to owning a diesel and just got a Sierra Crew Cab to pull my toyhauler. Yesterday, I got to 500 miles with no issues and decided to take it onto the highway to see how it did at high speed. I noticed that at 64 to 67 miles per hour I could hear and, to some degree feel, what seems to be a very low pitched howl or rumble from the front. It mostly goes away at higher speed and is not noticeable lower. I then ran at lower speed and by using tow haul mode was able to get the same noise at the same RPM. Definitely tied to RPM, not speed. Is this normal? Turbo maybe? Truck seems to perform well with lots of power (understatement) and no noticeable smoke.

<{POST_SNAPBACK}>

Curiuos, I know that GM changed the way that they balance the engine in late 2005 for 06 models. If it occurs regardless of throttle setting it tends to suggest a balancing issue but it if varies with power setting at stated RPM then it may be a injection timing issue. I would take it to a dealer and show them what it is doing (take them for a drive, just do not tell them about it.)

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I can't say whether power changes it but I will find out this weekend when I bring my trailer home. It seems to be in such a narrow RPM band that engine balance should be unlikely. It is a strange sound. Imagine a boom box holding a constant deep tone.

snoman · June 2, 2006

It seems to be in such a narrow RPM band that engine balance should be unlikely. It is a strange sound. Imagine a boom box holding a constant deep tone.

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Actually balance problem can be very RPM sensitive at times. YOu maybe be getting a resontance in your conbined intake and exhaust system which tends to look more possible here because such resonances are generally very narrow in range. Play with it somemore and track its behavior and if it is the same hot or cold too.