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High Pitched Whine
I have a 2008 Chevy 2500HD Duramax diesel with Allison transmission. When I am towing my 10M lb. fifth wheel camper on a steep grade, I sometimes hear a high-pitched whine after having been on the steep grade for some time. The whine goes away after I level out on flat ground. Is this normal and what is causing this extra noise?
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You may be hearing the turbocharger. If you had a boost pressure gauge, you may see a correlation between the whine and boost pressure. Otherwise, you could check the sealing of the airbox, air inlet ducting and related clamps for looseness.
Jim
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Boost Pressure Gauge
Is this an after market item?
This is my first diesel and I have a lot to learn.
Thank you.
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A boost gage is an aftermarket item. Not expensive, but requires some skill to install. Some kits allow for a tee to be used in a rubber line on earlier models, but yours doesn't have this option (no wastegate hose). You'll have to drill/tap somewhere in the intake charge-air side. No biggie, but no bolt-on, either.
Probably the turbo. As you start to pull a hill, the engine is relatively cool, as is the temps underhood (including intake air). As the hill goes on, things heat up and change the way the engine (and electronics) works to accommodate this. The turbo doesn't necessarily make more noise at higher power demands, but can, and does in most cases, have a boost/RPM/load range where it's most noticeable. Mine, for example, is most noisy (sounds like an F-16 winding up) at about 2,000 RPM's and between 8 and 12 PSI (max is about 30). The electronic controlled VGT turbos, like yours, will be similar if under like conditions, although much less noticeable with stock air intake. The condition is likely the computer adjusting the turbo performance under load. A sustained load, like ascending a grade, will allow the computer to normalize the entire system, and you may notice different noises than what you have become used to (even for short periods).
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Noise
Thank you for the explanation. I feel better about it now.
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It occurred to me that noise descriptions, like yours here, can be very subjective. Noises can't be heard through text. Anyway, another noise you may hear under load is the engine driven fan. Most often, it's described as a "roar", but could be a whine via the ears and description of some folks. Still, a normal condition.
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Noise
I think it is the turbocharger. I wish the manual would explain these things better. Thank you.
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