supercharger

I now have a sound immediately after getting out of hard acceleration that sounds like a screeching bark noise. I don't know whether it is from the transmission or clutch or engine. It will do it under stock fueling. It has had a similar noise since new, once in a while when the slack catches up when letting off in 6th gear. Today it was loud. Anyone have any leads as to what it might be?

VPI

I have recently noticed a noise that sound like one of those new VVT turbos slamming shut when I get out of the throttle. Wonder if this is the same noise?

hialtitude

That would be your turbo. Try not to do it too often.

supercharger

The noise is also there at 7lbs boost when I let off so it leads me to believe it is trans/clutch. Transmission has always been noisy, I figure something will break since I just turned 37k.

AK RAM

That is turbo surge, or stall, or bark (many names). Common and all turbos do it, but the bigger the turbo, the louder it will be. What is happening is your building boost, then suddenly letting off of the throttle creating a situation where all that boost is not needed any more. It exits the turbo from the direction it came since the turbo is no longer blowing at that moment because you let off the throttle. Path of least resistance thing. The bigger the blades, the more resistance, the louder it will be. If you have a big huffer, you can minimize it my being conscious of that fact and not let off of the throttle quite as instantly. Roll out of it a little slower. An alternative is removing the silencer ring. Don't know how that helps, but folks swear it does. Another alternative is adding a TAG. Not much good for anything else, but the TAG can really help with surge, if not eliminate it.

Bark can be really bad on my turbo as well with the automatic trans. Sticks are usually not as bad because you control the RPMs at all times. If I'm not paying attention, I can be accelerating in 3rd at 2K RPMs and get a very hard overdrive shift (RPMs drop from 2K to 1500), and this thing barks loud enough to wake up the dead. TAG is on the way.

Holset says that they test their turbos for 24 hours straight at 100% stall (yes, I to would like to know how they do that), tear them down, and see no ill effects from the surging. I don't buy it. It just sounds to bad when it happens, so I would try to keep it to a minimum.

bulabula

I can't say I've ever had any manual transmission bark or chirp at me, but certainly had my share of belts barking/chirping. I did have a manual tranny grenade itself but never chirp'd.

I've had motorcycle clutches make funny sounds when engaging, etc, but never an auto/trucks either.

Since you do have an '03, have you looked at your alternator bracket to see if its one of the ones that cracked? There's an old TSB on it, discusses belt chirp on shutdown.

Shovelhead

Turbo "Bark" is common under the circumstances you explained.
The turbo spinning at a gazillion RPM is trying to push air one direction while the unneeded boost is trying to go back through it in the other direction.
Under high boost, the rubber intake pipe connections can inflate like balloons.
That pressure has to go somewhere.

chrismez

Had that prob with the auto under hard acceleration when going into OD. Took out the silencer ring and it has not returned. I believe blow back through the turbo causes the blades to vibrate causing the noise.