Rattle/resonance - 2007 Suburban 1500

[arzinet]

Any TSBs for a rattle/resonance under hard acceleration on the NBS Suburbans?

 

When the engine is under heavy load (accelerating hard or pulling our trailer up a steep hill), I get a very loud rattling noise that seems to come from behind the passenger-side dash somewhere. It may also be coming from under the hood - that's what my wife thinks, but I'm not so sure...

 

It starts at about 1800 rpms, then goes away at around 2,000, until it comes back even worse between 3500-4000 rpms.

 

If I rev the engine in neutral, there's no noise. There's also no noise if I'm cruising on the highway at light throttle. When I am hard on the throttle and getting the noise, it goes away as soon as I lift off the throttle - even if the engine is still turning 3,500-4000 rpms.

 

I did a search, but only found that TSB about the A/C compressors on the older models. Probably doesn't apply to mine, anyway, but the rattle happens even when the A/C is off.

 

It's 100% repeatable, so I will take it to the dealer to have them listen to it, but it's always nice to go there armed with a bit of info.

[Magnumb]

No TSB that I could fond. May be catalytic converter heat sheid or manifold heat shield. Does is sound tinnie?

[C & A s Dad]

I hate to ask something so elementary and am not questioning your knowledge, but are you sure it is not detonation? Of course, if it is valve noise and detonation, it certainly should not be there and something is wrong.

 

What are you towing with it and how much does it weigh?

[C & A s Dad]

I hate to ask something so elementary and am not questioning your knowledge, but are you sure it is not detonation? Of course, if it is valve noise and detonation, it certainly should not be there and something is wrong.

 

What are you towing with it and how much does it weigh?

[arzinet]

No offence taken at the question, but it's definitely not detonation. I guess I should have described the sound better.

 

I've had loose heat shields on previous cars, and while this noise comes and goes in a similar way (according to RPMs), it isn't really "tinny" like that.

 

It's kind of a plasticky, rattling, buzzing kind of noise. Closest I can come to describing it is that it might sound like a coffee can full of plastic nuts and bolts sitting on top of a paint shaker going really, really fast. Don't know if that helps.

 

At first I thought it might just be the entire dash panel rattling, but putting my hand on it to try to stop the vibration didn't do anything. It really sounds to me like there is something hard and plastic, in or behind the dash on the passenger side, that vibrates at a certain frequency when the engine hits a certain RPM under heavy load.

 

BTW, the trailer is only a 21-foot travel trailer, with a dry weight of 3,800 lbs. I haven't weighed it, but I'd be surprised if it weighs much more than 5,000 lbs loaded. Just us, a couple of dogs, and a couple of bikes in the Suburban, so it's not loaded too heavily, either.

[03blackz71]

could it be the the air intake tube? Mine make a noise every so often. It is the parts that stick out from the main tube.

[arzinet]

Air intake sounds like a pretty good suggestion.

 

As far as I remember, it is plastic, and it is on the right side of the truck. Heavier load = more throttle = more air, so maybe that makes sense, too.

 

Maybe I'll pop the hood, have my wife rev the engine, and take a listen. Maybe I'll be able to hear something faintly, even if the engine isn't under load.

 

Thanks for all the suggestions, BTW. Keep 'em coming!