Seneca Cab Noise at Highway Speeds

[21stcenturymusclecar]

Originally Posted by Robbbyr

Shifter noise document, might help.

Thank You SO MUCH!!!!
Now if I can find out why these guys can’t find the part #s

JP

[Robbbyr]

Originally Posted by 21stcenturymusclecar

Thank You SO MUCH!!!!
Now if I can find out why these guys can’t find the part #s

JP

Hopefully the kit part # will still be available from Freightliner. The labor won't be covered by warranty obviously.

[memphis02]

Originally Posted by 21stcenturymusclecar

Was that the correct part in the Ebay link?

Could you please post that back, I can do the work

Thanks,
JP

After looking into it further, it did not appear to be.

[AZjayco]

Hello Columbo.... I am new to the group and have a 16 with the same issue... Did you find out if that was normal or what that is?

[AZjayco]

My 16 is at Freightliner now and they are saying the previous owner has the shifter bulletin done but mine is still making that noise and trying to pinpoint it... Any other ideas?

[Robbbyr]

Originally Posted by AZjayco

Hello Columbo.... I am new to the group and have a 16 with the same issue... Did you find out if that was normal or what that is?

Not Columbo, not sure if he participates much anymore. But welcome to the group!

In regards to your noise issue there are several things that could contribute to excessive cab noise.
1. Air passing over upper mirror bracket holes causing a distinctive whistle. Reduced by blocking off screw holes in the brackets.
2. Poor fitting doors allowing air to slip past the door gaskets. Reduced by aligning door(s), some have added extra gaskets too.
3. Sifter cable vibration. There is a TSB (technical service bulletin) applicable to early Senecas but I thought by the 2016 models Freightliner had incorporating the "fix" when they built them. But if the noise only is present when cruising and changes or disappears when you floor the accelerator it might be the cable.

There are many posts here in the forum, start by goung back in this thread to start with. You could also do search on "Seneca cab noise" and see other posts, some with picures of how we reduced the noise in ours.

Lastly, it is a big truck and less insulated than many cars, so some noise is expected. But once I had my shift cable fixed and covered my mirror bracket holes a conversation at 70 is no problem anymore.

If you need more help finding answers let us know. Many helpful owners are regulars here!

[AZjayco]

Thank you so much Rob.... I'm happy to be on here... It almost sounds like the howl is coming from the drive line. It starts at 50 and once I go over 68 mph or so it goes away completely even on the throttle... In the mph range when I let off the throttle all the way is disappears as well...

[Stargazerandu]

Third time camping in BlueBelle and each time I would tweak the cab whistling. This trip was whistle free. Conversation was effortless and I could hear the music and my GPS!! What a joy!!



Not only that but I filled the fiberglass cavity behind the cab seats with foam it green. My cab is cooler during this trip's higher temps, and I believe it helped with road noise. Oh, and I found a dead bee, the bee buzz that led to my discovery of the insulation void.



WHISTLE FREE!!! YEAH!!

[rgolding]

"Not only that but I filled the fiberglass cavity behind the cab seats with foam it green. My cab is cooler during this trip's higher temps, and I believe it helped with road noise. Oh, and I found a dead bee, the bee buzz that led to my discovery of the insulation void."

Could you talk about this a little more? Where is the cavity?

[Stargazerandu]

Originally Posted by rgolding

"Not only that but I filled the fiberglass cavity behind the cab seats with foam it green. My cab is cooler during this trip's higher temps, and I believe it helped with road noise. Oh, and I found a dead bee, the bee buzz that led to my discovery of the insulation void."

Could you talk about this a little more? Where is the cavity?

The cavity is behind both the driver and passenger seats, that wall. It's a fiberglass mold that shares an outside wall, a wall with no insulation. Also, on the floor of this void, there was an unsealed opening where I was feeling hot or cold drafts depending on the outside temp. I hope this helps...

[rgolding]

Thank you for the reply. So the un-insulated wall you are speaking of is behind the panel you are showing in the first picture? And you gained access to it by removing the panel you show in that picture? Great advice. So the insulate you used was a spray on foam like Great Stuff?

On my list of "to do's" is to insulate the backside of the steps and the stairwell.
If you look under your Seneca from the driver's side over to the steps, you will see it is a metal frame and the only insulate is the carpet is the stairwell.

In colder temps, this is a real heat sink and just draws in cold.

Always looking for ways to keep things more comfortable and quiet.

[RVermont]

The panel behind the driver is easy to remove simply pop the round cap off and remove the screws behind the caps. The one on the passenger side might be more troublesome. I had to pull the cabinet apart which was not difficult but I don't have the large unit with fireplace or tv.

Once in there you will want to caulk the seams as you can see right out those to the outside. I used ridged insulation and foamed it in place. Does deaden some of the noise.

Please post if you insulate the steps with details how you do it. I have trying to determine the best way to handle that area.