Is this normal

[Lazy_D]

Many of you have helped me along as a new owner and I appreciate it.
I have something else to throw at you all. I added a Acculevel to my pin box.
Now I notice what can best be described as flexing. It may be completely normal I just don't know since this is my first 5th wheel. In the video you can see when I hit a dip in the road my level and pin box doesn't move, but the front cap seems to have a lot of bounce in it as you can see if you watch the horizontal white pin stripe right above the level.
Thanks in advance.
Video 1
Video 2

[rhagfo]

dodge guy wrote:
In both pictures you can see the bolt hasn`t moved, but yet the bolt head is contacting the upper (cap or frame not sure) in the second picture with weight on it. this tells me the frame is flexing under the cap! I would definitely get in there and see what is moving!
I seem to recall frame issues on fifth wheels at the pinbox.
this isn`t as easy as just getting bigger bolts! if it was the bolt head and paint line would've moved with the weight on it, it didn`t.

I wouldn't tow that anywhere. something is ready to let go!

Great catch, and right you are, looks to move about 3/8" to 1/2".

[dodge_guy]

In both pictures you can see the bolt hasn`t moved, but yet the bolt head is contacting the upper (cap or frame not sure) in the second picture with weight on it. this tells me the frame is flexing under the cap! I would definitely get in there and see what is moving!
I seem to recall frame issues on fifth wheels at the pinbox.
this isn`t as easy as just getting bigger bolts! if it was the bolt head and paint line would've moved with the weight on it, it didn`t.

I wouldn't tow that anywhere. something is ready to let go!

[Old-Biscuit]

rhagfo wrote:

enblethen wrote:
The photos show the pin box is pivoting. The bolts are not tight enough.
Can you locate make and model of pin box? The installation instructions should show torque.
Looks like bolts could be 5/8 which need to be tightened to at least 160 ft lb or maybe 3/4 that need to be tighten to 210 minimum.
Trailair pin box instructions.

All of that, and in my eye the bolts currently holding it may not be the correct diameter, the empty bolt holes should line up, and they don't!

X2

If the bolts where the same size as the holes a lot of that movement would not be going on.
Bolts are wrong diameter.
And another bolt could/should be used in that middle hole front and bottom hole rear

[rhagfo]

enblethen wrote:
The photos show the pin box is pivoting. The bolts are not tight enough.
Can you locate make and model of pin box? The installation instructions should show torque.
Looks like bolts could be 5/8 which need to be tightened to at least 160 ft lb or maybe 3/4 that need to be tighten to 210 minimum.
Trailair pin box instructions.

All of that, and in my eye the bolts currently holding it may not be the correct diameter, the empty bolt holes should line up, and they don't!

[enblethen]

The photos show the pin box is pivoting. The bolts are not tight enough.
Can you locate make and model of pin box? The installation instructions should show torque.
Looks like bolts could be 5/8 which need to be tightened to at least 160 ft lb or maybe 3/4 that need to be tighten to 210 minimum.
Trailair pin box instructions.

[Lazy_D]

enblethen wrote:
Are the mounting bolts for the pin box inside the front cap?

No.

I took a picture of them with and with out weight.
You can also see how the holes don't line up and there is a visible paint line. I don't recall that paint line being visible when I bought it. And the bolts are all real tight.

With out weight



With weight on the pin


Pictures of the pin box mounting.

[enblethen]

Are the mounting bolts for the pin box inside the front cap?

[Lazy_D]

I measured the flex with weight loaded on the king pin. I took a 4X4 and jack and it measured out at 3/4". All the movement was coming from up inside the front cap. Not sure if that's to be expected on my unit. Will be passing that along to the dealership where I bought it this month.

[Old-Biscuit]

Hard to tell via video how much movement is from trailer suspension and how much is pinbox flex.


With piece of tape place a reference mark on front of cap above pin box.
Take measurement from fixed spot on pinbox to reference mark:
1. when hooked up and all weight on hitch
2. when unhooked and all weight on front landing gear legs.
3. watch for movement when making transition between the two.

Shouldn't be more than 3/8" difference between the two readings

If there is then you should remove overhang panel and visually check pinbox structure, sidewalls for cracks, tears, bad welds.
Repeat hooking/unhooking while inspecting.

[rhagfo]

TucsonJim wrote:
I see some of that with our FW, but not quite that much. I think it's worth investigation to make sure something is not wrong. I'd contact the FW manufacturer and send them the video to see what they think. Another option would be to share the video with your dealership's service manager and get their ideas on whether this is normal or not.

For that make and model of FW/chassis, it may or may not be normal, but I'd rather be safe than sorry. This is one of the times I'd rather listen to the pros, than rely on an internet forum for answers.

X2

[enblethen]

What kind of pin box do you have? If it is like an Airborne with the air bag it could be normal. Lower portion stays rigid but upper going through the air bag support flexes.
5th airborne pin box
I would check to insure the bolts holding the pin box to trailer frame are tight.

[TucsonJim]

I see some of that with our FW, but not quite that much. I think it's worth investigation to make sure something is not wrong. I'd contact the FW manufacturer and send them the video to see what they think. Another option would be to share the video with your dealership's service manager and get their ideas on whether this is normal or not.

For that make and model of FW/chassis, it may or may not be normal, but I'd rather be safe than sorry. This is one of the times I'd rather listen to the pros, than rely on an internet forum for answers.