Something worth mentioning..BOTH of my trucks had locking jaw problems in the winter. i dont know if it is a design flaw or what. Maybe Prime is putting too.much grease on the 5th wheels and it is sticking to the trailers.
In the winter, the grease can harden like caked mud and prevent the jaws from wrapping around the king pin completely. I asked youz guyz about this last winter with my old truck...lo and behold, this winter in my new truck it happened again. I backed under and the handle snapped, the jaws looked good...but when i pulled out the trailer dropped on my frame. another time i tried backing under three different trailers and it refused to lock completely. both times i had to get the pressure washer to shoot warm water on my 5th wheel and jaws. once cleaned, they both worked fine. so be careful how.much grease you use.
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The tug test is absolutely the first check performed immediately after hearing the unmistakable "ker-thick" of a positive couple. If that doesn't "pass", all other checks are pointless. I also tug one last time before releasing the tractor brakes.
Something to keep in mind during the winter months, our equipment is at times compromised from freezing temperatures and the accumulation of ice, snow and grime. Part of my winter pretrip is double checking the fifth wheel, testing to see how freely the unlocking lever will move. I believe the jaws did surround the Kingpin but never truly locked.
One of my final checks is to push on the unlocking lever to ensure there is zero play in it. Several weeks ago, during a sub-freezing cold spell, I had to force the lever by pushing it in to engage and lock. I am sure the freeze caused the "stickiness" requiring some extra coaxing.