nubbins_

Soooooooo............ I went for a drive with the SM, who seems surprisingly acquainted with both the current powertrains and RCSB trucks in general. He didn't end up feeling it, but suggested that if needed in the future, I could drop off the truck and he could drive it on the commute for two or three days to get a better chance of catching the transmission in the act of its stupid antics.

The highway vibration is 100% due to the tires. I got a set of 18" '15-17 PVD take-offs, with (peculiarly) a set of C-rated LT275/65R18 Goodyear Adventures on them, just to run for the weekend and test the vibration. I haven't seen this size on anything but HDPP, as unlike the LT245/70R17 Adventure, this one is a ProGrade tire with 3PMSF and 15/32nds of tread depth. Despite only being two pounds lighter than the Wildpeaks while being more than half an inch smaller and narrower too, they ride like a dream on the highway. Not the slightest inkling of vibration whatsoever.

Seeing as the Wildpeaks on the other hand are causing violent spasms on the highway throughout the entire truck, I'm going back to the tire shop next week with some serious questions about what the hell is wrong with the tire and their roadforce machines. We'll see where it goes from there. I'm also suspicious about the OEM 17" wheels, as I had the vibration persist even when I was on OEM Fortitude HTs, even after having the tires rebalanced and one of them replaced.

I'm still pretty adamant that the transmission is going crazy, but the guys at the dealership aren't unwilling to look at it further. It already has the 10R80 shifting TSB applied since early on, but both upshifting and especially downshifting in the gears 1-5 range is very shuddery, jerky and shaky, very often, in the city.

SM didn't seem to have heard of Falken much so I think it would be useful to point out here that I had a very positive prior experience with the same Wildpeaks in P265/75R16 on my last truck. It seems that these P285/70R17s have other ideas in mind.

MF cowboy

Has to be either the tires or the rims.
They are the only things that have changed.

nubbins_

I really want it to be the tires. Wheels would be a pain in the ***.

I went for a ride with my tire guy after the 3rd unsuccessful rebalancing attempt. The RFB machine read all green but none of the rebalancing had any effect on the shaking. He got a hold of some P285 Yokohama G015s as they are around the same price. Quieter tread, smoother tread, 30-day money back guarantee, and lighter weight. Win win.

Well, that is, if it's the tires. Tires and wheels are the only two possible culprits at this point in time. As I said to my tire guy while we were driving back to the shop, this whole ordeal is crazy since everybody loves their Wildpeaks and my past 265/75R16 Wildpeaks were impeccable too.

I love this truck more than anything else I've had because it's an RCSB, but I'm starting to reach my limit. The tailgate step is permanently warped from the post handle that wouldn't retract properly for a few weeks, and the block heater recall just turned into a second block heater recall, apparently. Now Ford is ripping out the evidently flammable block heater cord entirely until a fix can be found. Such is the state of Ford in 2019.

MF cowboy

Probably should get the rims checked either on a lathe or wheel balancer and put a dial indicator on the rim.
Maybe one of the rims is made off centre or really out of balance or something.

MF cowboy

When you do finally determine the exact cause Ford of Canada should be picking up the entire bill on this deal.

nubbins_

That's what I'm suspecting. It's rare for OEM rims to go wrong in manufacturing, and so much so that the road force balancing can't figure out how to eliminate it. And if it were the problem, most people agreed that I would have felt it at lower speeds too.

But like you said, it could be that one or more rims has a serious side to side imbalance, as opposed to along the rolling axis.

Oh, trust me. If it's indeed the wheels, Ford Corporate will have one angry customer on their hands. Literally everyone has taken the fall. Dealership replaced a stock tire and rebalanced the rest for naught. Tire shop is about to take the fall for a full set of Wildpeaks. I'm out $1100 on tires and a lot of gas money, and about to lose my patience and my sanity.