High Pitched Whine

[Cougar]

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?

[More Power]

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

[Cougar]

Is this an after market item?
This is my first diesel and I have a lot to learn.
Thank you.

[DmaxMaverick]

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).

[Cougar]

Thank you for the explanation. I feel better about it now.

[DmaxMaverick]

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.

[Cougar]

I think it is the turbocharger. I wish the manual would explain these things better. Thank you.

[JohnC]

I would call the noise from the turbo a whistle, or like a distant siren.

[Mark Rinker]

Turbo whine comes from firewall - if you open the rear slider window and the whine is coming from behind you, thats probably a pinion or u-joint bearing. Check all fluid levels in drivetrain.

[Cougar]

Hard to pinpoint the noise source location. Seemed like it was coming from the engine compartment.

[Mark Rinker]

Turbo, if you only hear it during acceleration and/or towing. Normal! Its a GOOD noise... :)

[MacDR50]

Got the same under the same conditions. High pitched whine right at the firewall. It changes with engine RPM and scared the BG's out of me. I thought maybe it was fan clutch slipping as the tranny was getting hot and I was going slow. Fan roar I know but this was much higher pitched. I asked around at the dealer and others and no one had a definite answer.

[jjcsnlynn]

I've only had the 'beast' for two weeks now and only driven it 4-5 times. This morning (as did the day I picked it up...35-45 degrees outside) there was a high pitched whine that mirrorred the engine RPM when the engine was cold. It only lasted for about 3 miles then went away.

To me it sounded like an alternator bearing, but I read something about a belt pulleys wearing out prematurely.

Any thoughts on what this can be. I'm still in my work clothes and may have to try to track down the noise Saturday morning.
;)