Lippert spec'd frame list

Absolutely correct. The boxed frame raises the frequency and decreases the amount of deflection, hopefully outside of the point of annoyance. Everything has a natural resonance frequency.

rskeans wrote:

Mile High wrote:
What is the big deal about frame flex? Frames need to flex somewhat, or the rest of the coach takes the brunt. The coach just needs to be designed correctly to account for the flex.

Well, my old '08 Ford had frame flex that would resonate around 45mph. When in resonates you get 'g' amplication that potentially could lead up greater problems. Not saying this happens here, but it could. Boxed frames like in the Chevy and RAM solve that problem. Also the frames used in the Mobile Suites and Lifestyle, and a couple others won't have that problem.

They all resonate. A boxed frame does not magically make this issue disappear. It might change the frequency but not eliminate it. All automobile manufactures have departments where there role is to minimize this phenomenon. It may be by attaching something to aid in cancelling out the response or designing it to a frequency that will hopefully be experienced less frequently.

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Cummins12V98 wrote:
The FACT is Lippert builds what the RV Mfg wants, in general that is "Light and Cheap" so most of the frame problems arise from that requirement!

Bottom line YA get what YA pay for!

Is that why you bought the cheapest of the big three trucks? why not buy the more expensive truck if you get what you pay for?

Actually yes! The wall broke a second time with the pin box...the problem was solved when we fixed the suspension on the truck...both times the pin box area was inspected and it was determined there was no flexing in that area.

All this occurred in the first four months of ownership....once the truck was repaired we lugged that unit around the country for another 5 and 1/2 years...never had another issue.

kakampers wrote:

colliehauler wrote:

kakampers wrote:

colliehauler wrote:

kakampers wrote:
Cracked walls are not always frame flex...our wall cracked in our Bighorn. The cause turned out to be broken welds in the aluminum wall studs...they broke due to our C4500 truck suspension and lack of air on the pin or the hitch. Absolutely nothing wrong with fiver frame...after fixing truck suspension and adding air pinbox, never had another problem.

What caused the welds to break, I would be willing to bet they were stressed from bumps. Why would they be stressed ? Maybe because the frame flexed enough to put stress on the wall joints. A air pin box absorbs a lot of energy. I stand by my statement the root cause was frame flex. A few years back a Toyhauler was built with not enough support for the pin box and they added a air pin box as well.

And in our case you would be wrong! There was no frame flex...in fact, the complete opposite. Our Kodiak, when it was sent out for up fit with air bags, they left the jounce pads on...the bags never functioned and it was riding on the pads...beat the******out of the fiver.

We had the jounce pads removed and added the air pin ourselves...manufacturer fixed the side wall only, never touched the frame..never had another problem...if it had been frame flex it would have happened again during the 80k miles we put on it...it didn't!

Didn't you have the air pin box for those 80k miles?

If I'm wrong it would not be the first time and probably not the last.

Are you seriously trying to say that a air pin box will stop damage from frame flex???

I'm seriously saying that a air pin box will absorb a lot of the shock that causes a frame around the pin box to flex. In fact a air pin box was used by a toy hauler mfg as a solution to pin box frame failures, they paid for the upgrade.

Did you have any more problems after you added the air pin box?

colliehauler wrote:

kakampers wrote:

colliehauler wrote:

kakampers wrote:
Cracked walls are not always frame flex...our wall cracked in our Bighorn. The cause turned out to be broken welds in the aluminum wall studs...they broke due to our C4500 truck suspension and lack of air on the pin or the hitch. Absolutely nothing wrong with fiver frame...after fixing truck suspension and adding air pinbox, never had another problem.

What caused the welds to break, I would be willing to bet they were stressed from bumps. Why would they be stressed ? Maybe because the frame flexed enough to put stress on the wall joints. A air pin box absorbs a lot of energy. I stand by my statement the root cause was frame flex. A few years back a Toyhauler was built with not enough support for the pin box and they added a air pin box as well.

And in our case you would be wrong! There was no frame flex...in fact, the complete opposite. Our Kodiak, when it was sent out for up fit with air bags, they left the jounce pads on...the bags never functioned and it was riding on the pads...beat the******out of the fiver.

We had the jounce pads removed and added the air pin ourselves...manufacturer fixed the side wall only, never touched the frame..never had another problem...if it had been frame flex it would have happened again during the 80k miles we put on it...it didn't!

Didn't you have the air pin box for those 80k miles?

If I'm wrong it would not be the first time and probably not the last.

Are you seriously trying to say that a air pin box will stop damage from frame flex???

kakampers wrote:

colliehauler wrote:

kakampers wrote:
Cracked walls are not always frame flex...our wall cracked in our Bighorn. The cause turned out to be broken welds in the aluminum wall studs...they broke due to our C4500 truck suspension and lack of air on the pin or the hitch. Absolutely nothing wrong with fiver frame...after fixing truck suspension and adding air pinbox, never had another problem.

What caused the welds to break, I would be willing to bet they were stressed from bumps. Why would they be stressed ? Maybe because the frame flexed enough to put stress on the wall joints. A air pin box absorbs a lot of energy. I stand by my statement the root cause was frame flex. A few years back a Toyhauler was built with not enough support for the pin box and they added a air pin box as well.

And in our case you would be wrong! There was no frame flex...in fact, the complete opposite. Our Kodiak, when it was sent out for up fit with air bags, they left the jounce pads on...the bags never functioned and it was riding on the pads...beat the******out of the fiver.

We had the jounce pads removed and added the air pin ourselves...manufacturer fixed the side wall only, never touched the frame..never had another problem...if it had been frame flex it would have happened again during the 80k miles we put on it...it didn't!

Didn't you have the air pin box for those 80k miles?

If I'm wrong it would not be the first time and probably not the last.

Mile High wrote:
I can tell you the fix from the Redwood and Montana factory was simply a cut in the wall below the slide with an H-channel trim inserted. Those that had them from the factory have not had issues. If it's frame flex, so what as long as you accommodate for the flex.

Now there is a big difference between frame flex and frame fail because of poor welds - different subject.

I know all you box frame lovers are compassionate about your box frames, to the point of it being a cult, but that isn't the only way to build a coach.

Our Bighorn and our current Landmark both had the cut with h channel trim...I agree, also not convinced boxed frame is the only way to go!

I can tell you the fix from the Redwood and Montana factory was simply a cut in the wall below the slide with an H-channel trim inserted. Those that had them from the factory have not had issues. If it's frame flex, so what as long as you accommodate for the flex.

Now there is a big difference between frame flex and frame fail because of poor welds - different subject.

I know all you box frame lovers are compassionate about your box frames, to the point of it being a cult, but that isn't the only way to build a coach.