QA1 CF driveshaft acoustics

[Zeromaz]

I have a 17 350R. It may make a difference in the R because it has no back seat and resonators but, i noticed after the cf driveshaft install its more resonant inside the vehicle at certain RPMs. The shaft feels awesome (lol) but it is pretty loud and i was wondering if anyone else has experienced this and if its normal.

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[Tractor Junk]

I’ve got the same shaft on the same car, and the acoustics are probably from the lash in the rear end. If you really want to crank up the volume, install aluminum diff bushings. Lots of knocking at low speed.

 

[Zeromaz]

Its like the car is humming loud on the inside of the car. Is this how yours is as well?

 

[GrabberBlue]

I would expect a CF shaft to have a reduction in NVH.

 

[Zeromaz]

I have only taken it to like 5k RPMs since it was installed and it seems to resonate loudly at 4k-ish. Below that its the norm acoustics, maybe a little quieter than stock.

Its not exactly a rattle like the car is shaking but maybe the best way to call it is that its like a subwoofer displacing the air in the car. Its that kinda rattle / humming

 

[honeybadger]

No noise that I can detect for me. But then again, HB is kind of loud.

 

[Zeromaz]

No noise that I can detect for me. But then again, HB is kind of loud.

Lol thats an understatement. She’s a real beaut Clark.

I think it wouldn’t be fair to compare. The HB is like a nuclearly mutated american rape dragon from another dimension.

The vibration / humming has me a little nervous because i wasn’t expecting that to happen.

 

[Tractor Junk]

When it’s humming, can you feel additional harmonics in the shifter? If not, it may not be the driveshaft. The exhaust has to be dropped to install the driveshaft, so it might be a loose exhaust clamp or heat shield buzzing.

I get a huge amount of gear whine through the driveshaft, but I also have solid bushings/ bearings everywhere and most of the carpet removed.

 

[Zeromaz]

When it’s humming, can you feel additional harmonics in the shifter? If not, it may not be the driveshaft. The exhaust has to be dropped to install the driveshaft, so it might be a loose exhaust clamp or heat shield buzzing.

I get a huge amount of gear whine through the driveshaft, but I also have solid bushings/ bearings everywhere and most of the carpet removed.

I’ll check again today but i didn’t notice anything particular to the shifter. It seems to resonate throughout the entire inside of the vehicle. Now that you mention added harmonics and the exhaust, i could see this being the issue. Is there a specific section of the exhaust i should look at?

 

[Mjc1241]

My CF driveshaft did that as well initially. Enough that I was concerned and took it back to the installer to check. I seemed to get a humming vibration at certain rpms in Sport mode. My CF driveshaft is from DSS just for reference. Had them put it on the lift to make sure everything was tight and lined up. Seems like the more I drove it, that same humming vibration went away and that has been over a year ago. I can't explain that one.

 

[Zeromaz]

My CF driveshaft did that as well initially. Enough that I was concerned and took it back to the installer to check. I seemed to get a humming vibration at certain rpms in Sport mode. My CF driveshaft is from DSS just for reference. Had them put it on the lift to make sure everything was tight and lined up. Seems like the more I drove it, that same humming vibration went away and that has been over a year ago. I can't explain that one.

Thats comforting. I’m about to take it out right now to see if i can narrow down the conditions it does this in. I’ll keep everyone posted and thank you for the reply

 

[Zeromaz]

Ok so. Wether or not the valves are open, it seems to only do it at exactly 4k RPMs. Didn’t seem as loud today though. The driveline isn’t shaking at all so i don’t think its anything dangerous. Its just reverberating at 4k. Maybe i should have gotten the driveshaft cored? Anyone else run their shaft with a foam core inside?

 

[GrabberBlue]

4k RPMs is the resonant frequency of the Voodoo (When it produces the most NVH). So it makes sense that you are experiencing the most noise then.

 

[Zeromaz]

4k RPMs is the resonant frequency of the Voodoo (When it produces the most NVH). So it makes sense that you are experiencing the most noise then.

You da man. You’re my heart’s resonant frequency. Thanks for putting me at ease

 

[Niz55]

No Boise for me. I also have a rear seat delete.

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