Nasty loud lift-off-throttle drivetrain noise HELP
 

Same noise whether the clutch is engaged or disengaged whether the trans is in gear or out of gear( or any combination of those 4. {pcfreak}

Any time I take my foot off the gas It lets out a Loud Harmonic howl .

If I left-foot-brake to slow down AND at the same time apply light throttle, the noise does not occur.

The car is 2 days new to me and it was just chassis-dyno. tuned at PRE in Portland Oregon. De-tuned from E85 to 92 octane. I do not know if it was doing this before it arrived there.

there is also a whine under light-cruise, but not Nearly as Loud as when I lift off the throttle.

It could be a lot of things.

Diff noise
Transfer case
Transmission


Your first step is to pinpoint noise origin. I.e left right front rear. And go from there.

1.) What clutch do you have
2.) is the noise more of a metal to metal like scraping/rubbing sound but the moment you step on the throttle the sound immediately goes away?
3.) Does this howl you speak of exist while you are driving and gets louder with increased speed whether applying throttle or releasing?

Sounds like noise is coming from the front of the car. If I had to guess towards the passenger side but towards the middle. That is certainly where the quieternal whine is coming from. (Which does get louder as speed increases, but that is nothing compared to the howl I am talking about.

1) I was told the car has an Exedy twin disk

2) that describes it well. I lift off gas, hear howl, metal on metal, sound immediately goes away when applying throttle. Every time.

It seems to happen when torque gets sent back into the transfer case from the wheels. Like when trying to engine-Brake going down hill. Except it even occurs on flat terrain while lifting off gas.

Howl does not change if I take car out of gear, put it back in gear while the clutch is depressed. Does not go away if I coast and depress clutch or engage clutch.

3) Howl does not occur while accelerating/driving whenever at least light throttle is applied. Howl does not occur while revving engine at a stop, with clutch in while in gear, or when clutch out with transmission out of gear.

3) It is louder dependent on speed I am going when I lift off throttle. I can accelerate from a standstill and never hear it. I also do not hear it if I shift quickly. It never gets louder/occurs when I am accelerating.

Thanks for the questions guys. I hope I am being clear in my responses. I appreciate the help. I look forward to your responses.

Transfer case i would say.

Have you looked under car? Maybe possible leak at tcase driveshaft input seal.

Have you done any fluids?

Maybe you should do trans gear oil and transfer case fluid.

Buy some 75w90 i believe. Try some lucas maybe you can bump it up to a 80w90 bump it up in viscosity a little bit.

No leaks. I will check fluid level later. I was told when I picked up the car that it had just been changed.

My last evo 8 that I owned I put 180,000 miles on the car. I am somewhat familiar with these cars and I have never run into this noise.

Soounds like a tcase.