5th wheel to Truck bed rails

[Dkentaz65]

My Curt hitch states min of 5 1/2 “ between the rig and my truck bed rails. I have the hitch as high as it goes and I have 5” clearance. Do I really need to adjust the king pin or do something else to get the additional 1/2”?

[rhagfo]

Lower the pin box!

[notanlines]

Yep, what Russ said. And 6" is even better than 5 1/2". When you lower the pin box, be sure to buy new grade 8 bolts, nuts and washers.

[chuckster57]

Originally Posted by notanlines

Yep, what Russ said. And 6" is even better than 5 1/2". When you lower the pin box, be sure to buy new grade 8 bolts, nuts and washers.

We have re used the bolts and washers for years without any failures. You do need to torque the nuts to about 350 lb ft. We also push up on the pin box as we tighten them.

[Roscommon48]

never heard of 350 pounds on torque.


here are the torques per etrailer.
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

[JRTJH]

Originally Posted by Roscommon48

never heard of 350 pounds on torque.


here are the torques per etrailer.
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

These are the torques per Lippert:

A. Torque 1/2” bolts to 110 ft-lbs minimum.
B. Torque 5/8” bolts to 160 ft-lbs minimum.
C. Torque 3/4” bolts to 210 ft-lbs minimum.

Page three of this document: https://lci-support-doc.s3.amazonaws...cd-0001721.pdf

Depending on where you get your instructions, which grade bolt you use (5 or 8) the torque values will change. There is also a torque variance depending on whether the threads are lubricated, zinc plated/dry or unplated/dry: https://www.fastenal.com/content/fed...0Gr8%20Gr9.pdf

[chuckster57]

I may have had the wrong information, my point is they need to be TIGHT. Your not going to get that with a standard 1/2 drive ratchet.

[flybouy]

Originally Posted by chuckster57

I may have had the wrong information, my point is they need to be TIGHT. Your not going to get that with a standard 1/2 drive ratchet.

At least a "moderate grunt"!

[gearhead]

You can't just throw out a torque value without stating what the conditions are: dry, zinc plated and dry, or plain and dry.
See if this link to Fastenal's values will open for you.
Note the notes at the bottom of the table regarding the "K" values and conditions.
https://www.fastenal.com/content/fed...0Gr8%20Gr9.pdf

Edit add: John beat me to it and I didn't see it.

[sourdough]

Originally Posted by flybouy

At least a "moderate grunt"!

Well, when I tried to tighten the ball nut on my hitch to 350lbs. with about a 36" long 3/4" drive ratchet and my feet shoving against the garage door frame, my body too made some strange "noises" but I don't know that I would call them a "grunt".....

[chuckster57]

Geez... I guess it’s my day to get ragged on.

No big deal, as long as I get a break in the next couple days.

I honestly don’t remember where I got that number from, it’s been a few years and a few pin boxes ago.