Interesting Info about 5th wheel Pin Box

[sandy43]

Whoever might be interested in the 5th wheel adapter (hitch or king pin). I'm in the process of changing out my TrailAir adapter (factory installed) and installing a Reese Goose Box. In doing so, I discovered the large 8 bolts holding it to the pin box was barely torqued at 60-80 lbs., and with 3-point bolts. This really got my attention, being I've been pulling this heavy RV around the country at 60-70 mph. I merely suggest everyone check those bolts for tightness. If your able, change them out for 8-point bolts and torque them properly. Think Safety.

[Tonkatoy77]

8-point or grade 8? I had to adjust my pin box after I brought it home. A couple of the bolts weren’t tight at all.

[notanlines]

I would suggest bypassing any grade 5 hardware and go straight for the grade 8. I tried retorquing our pin box a few months ago and all were snug. The Raptor box never loosened either.

[66joej]

If by point 3 you mean grade 3 we used those as shear pins. I am surprised specs would even allow bolts that soft to do the work of securing a kingpin that takes thousands of pounds pressure.

[Brentw]

Guessing here that he means bolts with 3 hash marks, these would be a grade 5. Should be the minimum strength on a pin box.

[sandy43]

My mistake. I meant grade #5 with 3 hash marks. I reckon you got the idea. Thanks

[rbrdriver]

So is grade 5 adequate then?

[Roscommon48]

you make reference to 'torque' but what would the torque specs be?

[66joej]

you make reference to 'torque' but what would the torque specs be?

Pin box bolt torque is based on the size of the bolts.

1/2 inch Bolts GR5 90 ft-lbs
5/8 inch Bolts GR5 150 ft-lbs
3/4 inch Bolts GR5 275 ft-lbs

[bobbecky]

It's interesting that bolt torques vary quite a bit. In the MORryde instructions for installing their pin box, they have torques for both grade 5 and 8 bolts. Our pin box came on the rig and had a mix of grade 5 and 8 bolts, but now have all grade 8. The torques recommended by MORryde are as follows:

1/2 X 13- grade 5, 65 ft lbs - grade 8, 80 ft lbs

5/8 X 11-grade 5, 135 ft lbs - grade 8, 170 ft lbs

3/4 X 10-grade 5, 220 ft lbs - grade 8, 280 ft lbs

The chart also stated all these torques were for zinc plated bolts, so there is a difference there too, between plated and not plated bolts as far as torque ratings.