Mystery "Twang" In Co-Pilot Area

[vicsryd]

I don't know if this is a Winnebago specific or Freightliner general problem so I flipped a coin and Winnebago won.

Starting a few months ago while driving down the road we occasionally hear a "TWANNNGGG" from under the floor in the co-pilot area. DW says she feels a a little thump then hears the twang (aka "THWANNGG"). The sound is like plucking a sizable spring with some tension on it (like a large guitar string) and having it hit something (the thump).

DW is pretty sure it comes from her center position forward and not from the suspension behind her. From the pilots perspective it seems to be coming from under the floor/stairs in front of the co-pilot. Some occurrences are louder than others and for these I can just barely feel the thump in my left foot on the floor in the cockpit and a little something through the steering wheel too. .

On a full day of driving the twang might happen twice and usually within a minute or two of each other. As near as I can tell it's not related to any specific road condition or hitting a bumped, etc. although it might be triggered by a harmonic. Most often it occurs while we are cruising down a smooth stretch of interstate. It happens with the stairwell cover opened or closed.

I've crawled, looked and touched everything from the front axle forward and can't find anything that is a likely candidate. At one time I suspected the step well cover mechanism because it has a taught cable/reel assembly. But so far I haven't been able recreate the problem while stationary.

Anyone else out there encounter something like this?

[vicsryd]

I don't know if this is a Winnebago specific or Freightliner general problem so I flipped a coin and Winnebago won.

Starting a few months ago while driving down the road we occasionally hear a "TWANNNGGG" from under the floor in the co-pilot area. DW says she feels a a little thump then hears the twang (aka "THWANNGG"). The sound is like plucking a sizable spring with some tension on it (like a large guitar string) and having it hit something (the thump).

DW is pretty sure it comes from her center position forward and not from the suspension behind her. From the pilots perspective it seems to be coming from under the floor/stairs in front of the co-pilot. Some occurrences are louder than others and for these I can just barely feel the thump in my left foot on the floor in the cockpit and a little something through the steering wheel too. .

On a full day of driving the twang might happen twice and usually within a minute or two of each other. As near as I can tell it's not related to any specific road condition or hitting a bumped, etc. although it might be triggered by a harmonic. Most often it occurs while we are cruising down a smooth stretch of interstate. It happens with the stairwell cover opened or closed.

I've crawled, looked and touched everything from the front axle forward and can't find anything that is a likely candidate. At one time I suspected the step well cover mechanism because it has a taught cable/reel assembly. But so far I haven't been able recreate the problem while stationary.

Anyone else out there encounter something like this?

[Gary CA]

Jon and Vicki: I have never heard a "twannnggg" but we have experienced "the thump". The thump made me stop off the road and scratch my head because everything looked good. I realized that a cross wind was causing the right front mud flap to thump the underside about where the passenger seat is.

That might be the "thump" still working on that "twannnggg thing".

[jimandsue60]

Could it be the mud flap hitting one of the levelor jack springs?

Jim

[MrTransistor]

Hi ,
On our 02 Journey, the passenger side shock top mounting bolt was loose and caused a 'thunk', 'thump', or 'clunk' sound. Freightliner tightened the mounting bolt and the noise was goon.

[MrTransistor]

Hi Vicki & Jon,

Same thing happened with the mud flap. It did have a kind of a 'twangggg' sound. Always with a right crosswind. I added a brace to the flap to solve this problem.

[vicsryd]

I had previously checked the HWH springs and the rear mud flap hitting anything. Nada.

Crawled around underneath again this time with DW sitting in the seat and step cover closed. Until your suggestions I hadn't considered the front metal debris/splash guard . Plucking it towards the rear with a couple of fingers make about the right noise but no thump. Then I realized the Kwikee step was extended (step off). Had DW retract it and did the test again. Sure enough, thump then twang. The guard was hitting part of the retracted step frame. DW confirmed the sound/feeling from the co-pilot perspective.

Given how rigid the metal is the event trigger is probably a harmonic being setup from the chassis and possibly the addition of just the right air pressure from forward motion and cross-winds.

Looking more closely I found only about 1/4" clearance between the guard and the step. I pulled back on the guard gingerly to bend it towards the rear a little and managed to increase the clearance to about 1/2". As added insurance I used Locktite liquid metal to glue a small piece of foam pipe insulation to the side of the Kwikee frame.

Manual testing says the problem is solved. We'll find out on the next trip starting 8/10 if works under driving conditions.

Thanks again for your suggestions to point me in the right direction.