I had the steering nibble esp. at 55-75. Good and strong. Dealer checked it out and said tires/wheels/ alignment ok, it's the rack and pinion and the sbn would cover it. Only they were on back order and making a new one since the sbn one was not curing it.
I could not see how gears could care about temperature and air pressure, so I went somewhere else-Discount Tires.
I told them the story, they told me some. Bottom line, one of the front tires was out -road tested- some 48 lbs. The rest were fine. They did what they could which brought it down to 26 lbs. and put it on the back axle. I drove down the highway and the steering nibble was gone, but I could feel pulsing in the gas peddle. I bought 4 new tires, had them balanced and road tested and I watched which meant that one of the new tires was returned for another and now I have no steering nibble and no gas peddle vibration.
I did learn that not only can they measure your tires, but you need to watch it and not be happy with a 26 lb even though the manufacturer says its ok.
Apparently with the new F150, it is not.
Good luck.

 

What are you talking about?

 

road force balancing

 

Is that 26 lbs of wheel weight? Isnt tha a lot ?

 

The road force test can check out the un-balance of your tires, not only the standard old fashioned way, but the balance of the left side of the tire from the right side of the tire. They can spot where rubber is too thick or too thin and so causes a pound force of thump on one side of the wheel when it hits the pavement. In my case, one side of one tire was 48 lbs out. That means when one point in that tire circled to the pavement, it hit with 48 lbs more than the other part of the tire.

Google 'road force tire balance' and you'll learn all about it.

It was dead on because I had the nibble in the front and the bad tire was in the front. When they 'fixed' it as well as possible and put it on the rear, I had a vibration in the gas pedal (not one before).
And now I have new tires and no nibble and no gas pedal vibration. I watched the road force testing and one of the new tires flunked!!! So they put another one on and it passed with flying colors.
Road 150 miles today and no nibble and no vibration anywhere except on bumps. I had the nibble at 55-75 mph. And read every thread. When the outside temp seemed to make a different I decided that it couldn't be the rack and pinion., it had to be the tires or wheels.
ps this road force balance will tell about the wheels as well.
And ppss, the dealer said my tires/ wheels were great.
!
So much for that.

 

I had the intermittent steering nibble over 60 mph as well. Mine seems to be tire related, as it started immediately after the first rotation at 5,000 miles, went away after the 10,000 mile rotation and started to come back at around 16,000 miles, again going away after rotating. I have the 18-inch BF Goodrich passenger rated tires.