[ds968]

This is on the tiptronic car . After I accelerate and then lift off the gas pedal, there is a metallic whirr / buzz sound which lasts for a few seconds, and which emanates from the rear of the car. Not a rattle, no clanking, just a very uniform resonating metallic sound . Here's the interesting part : this ONLY happens between the 60 mph and 70 mph segment . If I drive below 60 mph and do that, there is no sound . If I drive above 70 mph and do that there is no sound ..until it gets down to 70 mph and then it makes the noise only until it drops to 60 mph and suddenly ceases at that point . Any ideas ??!

I almost want to say it sounds like the catalytic converter buzzing I heard many years ago on my 944s when it went bad, but IIRC , that happened all the time on deceleration, not just between 60-70 mph.

What could it be ?

Partial Post: Please Login or Register to read the full post.

[Kim]

perhaps a speed-specific catalytic converter or muffler heat shield?

Partial Post: Please Login or Register to read the full post.

[MCL968]

Maybe a loose center cap on a wheel? If not that, or a resonating heat shield, I would replace the muffler bearings and the piston return springs.

Partial Post: Please Login or Register to read the full post.

[flash]

i'm going with the chrome kanuter valve

Partial Post: Please Login or Register to read the full post.

[ds968]

Huh ? What the hell is a " chrome kanuter valve " ?!

And along the same lines, what are " piston return springs " ?!

Partial Post: Please Login or Register to read the full post.

[MCL968]

You may be right, I have an early 92 and my kanuter valve is plastic and can't be rebuilt. If he has a chrome unit, he might get away with just having it reground.

 

Dan, ask the guy who rebuilt your engine if he ground or replaced your kanuter valve when he reinstalled the engine.  

Partial Post: Please Login or Register to read the full post.

[az968]

My kaunter valve started acting up on the long drive back from Tahoe, drove me batty cause I was accellarating and decelerating all the time. I was able to regrind mine and all is good now.


You might also check for a loose rock in the hubcaps.

Partial Post: Please Login or Register to read the full post.

[ds968]

Thanks, MCL, I'll ask him .


Nothing out of place re the caps .

Partial Post: Please Login or Register to read the full post.

[Waylander]

Oh My

 

https://www.quora.com/What-is-a-kanuter-valve

Partial Post: Please Login or Register to read the full post.

[az968]

Sermiously, check the rear wheels for balance and tread issues.
Sermiously, check the rear wheels for balance and tread issues.

Partial Post: Please Login or Register to read the full post.

[ds968]

Oh My

 

https://www.quora.com/What-is-a-kanuter-valve

Ha, fell for that . I'll find a way to get back at you friggin' clowns later but right now I have to go and refill the headlights fluid container . That might explain why the high beam is dim.

Partial Post: Please Login or Register to read the full post.

[ds968]

Sermiously, check the rear wheels for balance and tread issues.Sermiously, check the rear wheels for balance and tread issues.

I don't think that would make a metallic sound resonance - this sounds a lot like a heat shield , or heavens forbid a transmission plate ( although the latter would make noise at all levels not just between 60-70 mph )

Partial Post: Please Login or Register to read the full post.

[flash]

i'd ask donald trump, but he'd probably just blame hillary.  wait!  maybe it is donald trump.  you said it was coming from the ass of the car, right?  

Partial Post: Please Login or Register to read the full post.

[968Syncro]

My car, tiptronic, used to make a "whirring" sound, almost like a jet airplane whirring / whining, but no "buzzing" associated with it.   Sounded like it was from the trans.   Not sure if your sound is similar.  Nothing every happened, didn't make a repair.  Now it has been gone for some time, this post simply reminded me that it was once there.

 

On the other "suggestions", some time ago when took someone new on a backpacking trip, we'd always instructed them to bring a "left handed smoke shifter".

Partial Post: Please Login or Register to read the full post.

[az968]

Dan, is it speed related,which which is why i thought could be wheels, or is it RPM related? Have you tried to see what happen at the same RPM but in lower gears?

Partial Post: Please Login or Register to read the full post.

[ds968]

Interesting , I never looked at the rpms. Will do that today . Although, and with the disclaimer that I know only little about tires , I can't imagine there's any possibility they would produce a distinctly METALLIC resonance sound no matter what may be wrong with them .

Partial Post: Please Login or Register to read the full post.

[ds968]

I think I found the culprit . I let the car idle for a while until it warmed up this morning , and then while parked I revved it up and let the rpm drop ( multiple times ..) sure enough, that buzzing / resonance is there even when the car is stationary. Even while idling there is a more muted but still audible metallic resonance , so I got a pair of gloves and just out of curiosity nudged the muffler up and down a little to see if the noise would change in any way . No change if I push the muffler up, but the moment I pull it down just a little , the noise stops right away ! Heat shield I presume ?

Partial Post: Please Login or Register to read the full post.

[MCL968]

Possibly, but I would guess there is a plate in the muffler that is the culprit.

 

If you want a cheap temporary fix, locate the spot welds on the body of the muffler and hit a few of them with a centerpunch and a hammer. A small dimple may solve the problem, which is ironic since dimples always got me into trouble.

 

M-

Partial Post: Please Login or Register to read the full post.

[ds968]

I checked the muffler heat shield this morning, and it feels solidly in place all around , there is also plenty of clearance ( as far as I could see and feel ) between it and the muffler so I can't imagine it's touching anywhere when the exhaust / muffler vibrates on deceleration .

Still, between 1200 rpm and 1800 rpm the resonance sound is far more pronounced , and then becomes almost inaudible either below or above those thresholds . Very similar to that 60-70 mph segment symptom on declaration . It's also louder when the car is very warm , as opposed to early morning after a cold start . I tapped the muffler spot welds and the body of the muffler itself ( when cold ) and could not hear any sound indicative of something loose. But clearly something is either touching somewhere, or maybe something is loose inside the muffler itself, because as I mentioned before, with the car idling if I just slightly pull the muffler down the noise stops .

Partial Post: Please Login or Register to read the full post.

[az968]

Did you check the bracket that holds the muffler at the tailpipe ends? Maybe the rubber gussets are failing.

Partial Post: Please Login or Register to read the full post.