King Pin box shifting

I am a bit concerned about the king pin box shifting. I noticed it when we stopped at my sister's to visit. I loosened up all the bolts and repositioned the king pin and re-torqued all of the bolts to 70 lbft., which is what the manual says to torque them to. When I towed the rig to dump the holding tanks, I noticed that they had shifted again. It seems that the proper torque is not tight enough to keep the king pin from shifting. Is the manual incorrect and does it need to be changed? Upon closer inspection I also noticed that all of the bolts holding the king pin are grade 5. I am not an engineer or an expert, by any means, but it was my understanding that DOT requires grade 8 bolts in all critical connections. I would say that the king pin qualifies for that. Clarification from the factory would be greatly appreciated.

Oldleatherneckgirl,

I was told when I put on the Mor/ryde pin box to tighten the bolts to 120ft# by Mor/ryde. Thats all I know at this time. Bob

If you double what you've been doing, your pretty close.
I tried to upload a chart for you, but the formating got messed up.
TimK

Try this link http://www.raskcycle.com/techtip/webdoc14.html

Thanks everybody, appreciate the responses.

I've noticed the same problem... The give away was looking at the un-used bolt holes... one can see that the hitch pin box has shifted.

I've been considering changing the bolts... to a size that will FILL the holes completely... seems the shift will happen if there is a little too much movement between the bolt and the surrounding hole.