WOW how big is your fresh water tank and where is it located? Also I don't see that you have weighed your rig, without those numbers you are just chasing your tail.

 

I think that's how mine felt before I got enough force on the WDH. But you said you cranked on it already, so maybe the problem is elsewhere. I would have a good suspension mechanic go over the whole thing from axle to axle.

 

Having a passing truck push the trailer and turn the truck into the passing semi is pretty normal. It's a good indication that your sway control is doing something since it is turning the whole rig as a unit rather than just pushing the trailer to the side behind the truck.

you will likely notice that you have to steer "downwind" in a crosswind as well. Another indication that the truck and trailer are acting as a unit rather than as two separate vehicles attached by a round ball.

 

Your best course of action at this point has been suggested several times already, take your truck and trailer, packed like you are heading out camping, to a truck scale and get all of your weights verified. On a 3 pad scale (like a CAT scale) get the steer, drive and trailer axle(s) weights with the truck and trailer hitched and WD engaged, then another weight reading with the combo hitched but WD bars disengaged and then a third weight of just the truck by itself. All these weigh-in will cost you about $15 or less and will give you the info you need to properly make adjustments based on the factual weights, not guesses and estimations. Post those weights up here and we can suggest the right moves to make with the truck, trailer and hitch. If you can, post a side view picture of the truck and trailer hitched up with the WD set how you think it tows best, and another of just the unhitched truck, there may be some visual clues to help the group here give better advice since the truck has modified suspension. Give us the info on the WD hitch being used, brand, model and weight rating of the spring bars and if it has built-in sway control or any other add-on sway control devices.
What pressures are you running in your tires? All of them, front, rear and trailer, improper tire inflation can cause some of the handling issues you have described. Are the truck tires Load Range E?
What is the size, load rating, max speed rating, max pressure, brand and age of the trailer tires? Typical Chinese trailer tires have a max speed rating of 65 MPH, exceeding that speed, especially in high heat or low inflation (which increases the tire heat) greatly increases the risk of tire failure. Some newer trailer tires, even some of the Chinese ones are now showing higher max speed ratings as well as the USA made Goodyear Endurance ST tires. Cheap Chinese ST tires should not be expected to last more than 3 years in service, the better ones may be able to go a bit longer.
1000lbs of fresh water! Wow, that is a big fresh water tank at 125 gallons, our old TH had a 120 gallon tank and I thought that thing was massive!

 

You are feeling the bow wave effect when the trucks pass you.The only thing you can do is make sure your w/d is set up properly,you will never completely get rid of it. The issue is caused by air pushing on the side of your TT, you can feel the same thing in your passenger car as a semi goes by but to a much less degree,since the car less surface area for the air to push on.

My TT does the same I have got it better but is still there,The Hensley hitch will help a lot also

 

Excellent video explaining sway.

 

Absolutely Excellent video.....thanks for posting it!

 

It is a good video. I watched the entire thing. It seems like it should be part 1 of 2. A lot of trailer sway can be attributed to improper weight distribution in the trailer itself. Sway often manifests itself when there is an insufficient ratio of weight on the tongue.

For my toy hauler I wasn't getting enough weight on the tongue with the ATV (2013 Ranger 900XP around 1,400 lbs) pulled in forward. That put the engine at the back of the trailer. When I pulled the ATV in backwards that fixed the tongue weight problem as the engine was more over the trailer's axles instead of hanging out so far to the rear.

 

I agree with you Jim....Toy Haulers are a whole different breed when it comes to tongue weight and getting enough of it. When I bought mine new and towed it home, it towed perfectly...empty! 9000 lbs of trailer and approx. 1350 lbs of tongue weight, which is right at 15%. Once I got it loaded, especially hauling two motorcycles, and everything that I took to the track....toolboxes, paddock stands, EZ up, weights for the EZ up, spare tires and wheels, etc., I no longer had anywhere near enough tongue weight and the amount of sway was horrible.....and that's with the Blue Ox WDH. Tongue weight was just slightly under 10% loaded like that. I started adding weight to the front of the trailer.....two batteries vs. one, a 35 lb barbell plate, 60 lb sand tubes, and running with a full 106 gallon fresh water tank. I finally got back up to right at 11.5% tongue weight and it tows fine now. Like I said, Toy Haulers are a different breed to deal with and may require several scale trips to get everything correct.