A PinBox safety question-

[Matt400]

Currently I have 10 bolts holding the hitch pin to the box assembly on my 5th wheel which has a GVW of just under 14K.

I would like to lower the pin assembly down one notch for better bed clearance but doing this will leave 8 bolts, 4 on each side.



I think it would be fine but the idea of leaving 2 out because there wont be a slot for them feels odd so thought I would ask.

 

[MAleshire]

I think using the eight bolts would be just fine. However, if I were doing that job, I would call a shop that specializes in hitches and ask. To be real sure I'd call the tech line for the 5th wheel manufacturer. Most of the manufacturers also have web sites for technical questions. I'm going to be going through the same process shortly. I've been pulling my 5th wheel with a Ford Power Stroke, and now have the hitch in my Dodge CTD. The trailer is stored about 50 miles away, and just from looking at the bed on the Dodge I think I'm going to have to lower the King Pin and raise the hitch plate to get proper clearance. Be sure to get the proper torque specs.



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[jelag]

Look at the grade of bolt used... a grade 5 bolt as an example has 3 hash marks on the head... a grade 8 has 6 and so on... .

The shear strength of a grade 5 is marginal the way I see it... . the shear strength on a grade 8 is almost twice the amount as a grade 5... . Also remember that 10 grade 5 or lower bolts might be cheaper than 8 grade 8 bolts to assemble... that might be the driving factor...

My 5er that has 8 bolts, weighs 12K with grade 8 bolts and I'm not worried... and I'd let that go to 16-18K lbs as well...

If you look at some industrial trailers with a pintle hitch you can see an adapter to move the ring on the trailer up and down... there are usually 6 bolts, 3 on each side... usually 5/8" or 3/4" grade 8... and these trailers can go to 25 or 26K lbs based on the axles...

But you have to be comfortable, as we're just giving you our input... if you don't think its safe do something else...

 

[Matt400]

I did call the pin box manufacture today and they felt leaving 2 out was ok.

 

[Jim W]

I would replace your bolts with new bolts that are of the same size but at least grade 8. When bolts are torqued and these may have been over torqued they stretch, thus necking down in the thread area. These bolts are placed in shear and you need all of the area possible to carry the shear load. Just a suggestion. I would go to a equipment dealer to buy the bolts and nuts, I would also suggest that you buy plated bolts so you do not have to worry about rust.

 

[icman95]

I'm with everyone else. My first thought was to go with grade 8 bolts if you're going to do it at all. There may have been grade 8's in there to begin with, but it couldn't hurt to change them out for new ones just to make sure. Also couldn't hurt to buy stainless. Might cost a bit more per bolt, but worth it in the long run for such an important area.