This is what I would be examining as well. Has this height changed between the '04 and the '15?

 

Sounds like you're talking to some idiot service guys...maybe find different ones?

Remember the 2015's are a hell of a sight lighter than the older ones, too, so the trailer-to-truck weight ratio isn't the same. The trailer's going to bully the truck a little bit more than it did the 2014.

It'd probably be a pain to coordinate, but you could try hooking the trailer up to another F150 like yours, see if you have the same issue.

I'm sure someone on here will point things straight for you.

 

yes I checked, and changed hitch settings many times.
I did try another F15o, towing fine behind my 2004

 

before we jump to blaming idiot service guys...

given how many members here are towing happily and successfully without this issue, it seems fairly logical that the issue is somewhere in your trailer set up. Just because it worked in one configuration on your 2004, doesn't mean it will work in the same config on a 2015. Normally with different vehicles you need to find the sweet spot of tongue weight and weight distribution on the trailer.

Also you dont mention whether it is the same wb/cab configuration on both vehicles and, as pointed out below, are you using a wdh?

Not quite sure what you could reasonably expect Customer service to tell you over the phone without seeing and having details of your set-up.?

Would you expect a doctor to diagnose and fix a broken leg over the phone???

 

We are having the same issue with our truck right now. We bought a 2015 Ford F-150 XL Sport (cab and a half) with a 5.0 L engine, 3.55 rear end. Our travel trailer is 5,500 lbs. We used to have a 2005 Ford F-150 XLT (supercrew)with a 5.4 L engine that pulled the travel trailer just fine. Never had any problems. But with this new truck, it sways. My husband said that he can not relax when he's driving like he could with the old truck. My husband has tried everything that everyone has suggested here, but it's still doing it.

So, we were wondering if you were ever able to get your situation figured out and if so, how did you do it?

Thank you.

 

The height from the ground to the center-point (horizontal) of the receiver is higher on the newer F150.
When I moved from my 2010 to an identical 2015, I had a lot of sway. I had the hitch head lowered one step lower. That did the trick!

 

I believe it's just a function of a much lighter truck. The front end just doesn't put the same amount of weight on the front tires. I lowered the wdh and helped a bit but grabbing one more link on the chains (ie more weight on the front tires) makes it better.
I was going to try going up one size of hitch to 1000lb from my 800lb bars to see if that would help.

 

Sounds like the tongue of the trailer is too high on the newer truck. Drop the ball down enough to nose down the trailer and get a wdh setup to level it out correctly.

My 5.0 tows my 6k lb Trailer with zero issues after I adjusted everything correctly.

 

I think these trucks need more tongue weight. I notice that the more crap I put in the bed of the truck and front of trailer the better it tows

 

I had to make adjustments as well moving from a 2013 to a 15. The 15 is definitely higher in the back.
I had to tilt my ball towards the back so I would have a min of 4 or 5 links of chain when I got the WDH to the perfect set up.
Lots of trial an error.
I would also suggest take you truck and trailer to a RV shop and have them do the setup for you.

I hope you get it sorted out

Happy camping