Let me qualify my remarks by stating I spent 27 years in the Coast Guard and participated in several accident investigations where towing was involved. Most large boats are tail heavy and the trailers are very long. When a large dip in the road is hit, the boat trailer tries to pick up the rear end of the tow vehicle. The Coast Guard had several wrecks do to vehicle loss of control after a large dip in the road was encountered. I believe in your case the trailer coupler has enough wear that it popped off the ball rather than lifting the rear end of the tow vehicle off of the ground. The fix is replace the trailer tow coupler but then be aware that the trailer will be in a better position to lift the rear of the tow vehicle off of the ground in the future. Less speed will reduce the leverage the trailer will place on the rear of the tow vehicle.

 

One of the things I have not seen in any post is the lubing of the coupler assy. & ball.
If the finger that fits on the under side of the ball dose not move freely can cause issues.


Beside the grease will slow down any wear of coupler & ball and make it easier when making turns as it will pivot and not try and force everything to go straight.
This is a big deal to grease 5th wheels for turning.
Dave ----

 

Not my personal experience but I passed a guy the other day up in PA with a homemade enclosed trailer with a broken coupler. The trailer looked like a camper chassis with those old big four lug Fayette wheels with about a 26' truck body on it. I pulled up next to the guy to see if he needed help and he said he not unless I've got a coupler and a welder in the trunk. The ball had worn into the couple so bad it finally just ripped the front of the coupler open and slipped off the ball. I have no idea what was in the traler but a guy stopped with a 2 ton jack and it wouldn't lift the tongue of the trailer off the ground. He said he moved over to the right to go around a car making a turn and when the trailer hit the soft shoulder it ripped free of the ball.
I didn't see it happen but I didn't see any safety chains. It looked like he wasn't going very fast and the soft dirt and asphalt there stopped it quickly right behind his van.
I think basically it was a case of a cheap stamped coupler pulling about five times what it was rated for.

 

I know the thread is old; just reading it though.

I always spray WD-40 on the ball and coupler before I use it (5 ton dual axle utility trailer - 2 5/16 ball). Makes everything so much easier, including the coupler seating on the ball solidly.

 

The thread is old, yes. I just wanted to pass this on, beware of WD-40. When it breaks down over time, it breaks down into a tacky paste that attracts and holds dirt. Yes it's wonderful for quick fixes and rusted stuff. But use silicone for long term incremental maintenance. When it breaks down, it does so clean. If your a real nut, like me, use food grade silicone.

And years ago I was towing a 35' Hatteras on a gooseneck cradle. I ran over a 2x4 at 45-50 and the hitch came loose in the bed. Saftey chains saved the day but destroyed my Silverado bed. Not to mention it likely has something to do with the reason I'm bald

 

I typically spray the hitch ball with WD40 (because its handy and a good cleaner) and then wipe it clean with a shop towel. Then give the ball a quick squirt with white lithium grease before connecting the trailer. When I disconnect I wipe the ball clean again, put the ball cover on and, if I am not using the trailer again soon, remove and store the drawbar and ball. Keeps the ball and hitch like new and rust free.