when I had the leveling kit removed and struts replaced I had them check the rear springs as well and they said everything looked good. I’m not even sure how often to replace leafs. I have 88,000 miles

 

The HDDP F150's do come with upgraded REAR springs and SHOCKS besides upgraded front springs to. Upgrading to 5100 on the rear are the equivalent to our stock shocks.

 

Okay, the measurements look about right. The only thing I can think is the tongue is to light and/or all the weight behind the axles is causing it to teeter totter. Like I said I pulled a 7000GVWR Enclosed Car Hauler (My little travel trailer is only 5500 lb) with 6500 GVWR / 4700 lb Curb Supercab and had no issues. An HPP is at least 50% more truck (in my opinion) and we have guys pulling 9000-11000 lb travel trailers in the HPP without the issue although I have no idea how long it took them to get the correct set-up.

I'm going to shut up and let a toy hauler expert try to help. I'm stumped beyond that.

 

Alright, here's your issue. 1200 pound bars, with 900 pounds of TW is a no no. Been there, Done that. You need to get weight on the tongue at least to 1050 or more before those springs will do their job. First, if you are really light, and 900 is really light, the springs will cause the nose of the trailer to rise and fall with every dip in the road, after all, they are springs, AND more important, they lack sway control. In order to get proper sway control the bars need to apply a specific amount of force to the hitch head, which can't be accomplished without raising the back of the truck above it's distribution point, making the rear axle too light and the front axle too heavy. So either get as much weight up on the ball as you can, or reduce the spring bars to 1000#.

You don't need band aids on the truck, you don't need a 3/4 ton, you just need to get the distribution corrected, or replace the spring bars to match the TW. This is the most common reason for porpoising, improperly set up or wrong type equipment.

 

this is awesome thank you so much!

 

After I got my F150 HDPP I still had a Flagstaff 26wfkss tag trailer and had the same or similar problem. The numbers with it were 29'-10" about 7100# loaded and 720 tongue weight on my previous TV. I was using an Equal-i-zer hitch but with 1000# bars. Going over every dip and sway in the roadway the trailer would want to dive and surface. With the advice of a few kind brothers here ( https://www.f150forum.com/f82/first-...set-up-429663/ ) I got sorted. The first thing you need is be sure the trailer is at least level (with a level on level ground) or slightly nose down or you will fight it. By removing one or two washers, I think I had three in, and adjusting the bar tension along with putting more weight on the tongue I was able to smooth it out. Also adding Bilstien 5100 rear shocks and a quarry nearby that allows me to use their scale on Sundays helped.

 

Couldn’t possibly be the truck, has to be the hitch. But you were fine with a truck with adequate suspension though. Yep has to be the hitch.

 

Have to disagree with you on this one. His symptoms point to an improper set up. Porpoising 9 times out of 10 is a bad set up, the tenth is usually more trailer than truck, but that doesn't appear to be the case here. He has the truck to handle th TW, he just needs to get the TW up there,

 

Porpoising (Pitching)is generally caused by the trailer teetering forward and aft on its suspension. If the TV is unable to adequately control and dampen those forces from the trailer the TV suspension is inadequate and makes matters worse. You can try to stiffen up the TV rear suspension by installing higher rated WD bars but the solution is really to change the loading in the trailer and/or get a TV that has adequate suspension. Toy haulers by design will have a tendency to pitch due too high weight forward to compensate for the anticipated load added to the rear. From a trailer design standpoint that’s a less than ideal weight distribution that the TV has to overcome and control. Even though he is within ratings of the TV specs he needs the added control of a higher class truck.

 

You need much more tongue weight. Simple as that.

As for overheating, get the truck hot and measure the inlet and outlet of the radiator with an infrared temperature gun. Should be around a 50F degree drop coming out or the radiator is faulty.
Is your truck a 53A as well as HDPP? If not, and I am sure someone knows, but I dont know if that year truck came with cooling upgrades without at least being a 53A. 53B of that year might not have the upgraded radiator. 2018+ 53B trucks got all the cooling upgrades of 53A.

Long story short you may need a radiator upgrade.