Tug test is not a check for connection, it is a brake check

so how do you find this during a pre trip?

 

Time to retire that beast and send it to the scrapyard!

 

You do both! Visual test and a tug test!

 

Both a tug test and a visual jaw & gap test only suggest a good connection.

A typical tug test is useless if the load is heavy unless you tug very hard.

At least a half-dozen times I've almost dropped a trailer that was resting on the fifth wheel plate and jaws closed. If you try to hook a trailer that is slightly higher than it should be and you are off-center when you back into it, your kingpin can force the jaws closed but they will open when you pull forward.

Anyone that has ever had a trailer not latch, no matter how hard you back into it, is often going to look appropriately hooked but not be good to get on the road.

 

My fifth wheel doesn't even have jaws. It has a bar that slides behind the kingpin into the other side of the fifth wheel. When it's locked, it's locked.

 

I had a fifth wheel refuse to lock on a trailer once after two tries I pulled ahead
to have a look. There was a flat metal ring the kind that holds a flat Teflon lube
disc in place squished around the pin. The last truck to pull that trailer must have
had enough wear on the jaws to let them close.