I know there are lots of threads on vibrations, but we rarely hear about a success story.
2017 XLT CrewCab, 3.5 eco 157"

I had the vibration during coasting. It would start at around 54mph and go through 45 then disappear. It would feel like driving over a really rough road or small strips across the road. I put up with it for about a year or so and realized it was getting worse. I took it to the dealer and made sure they understood exactly what I was feeling and that I thought it was either the drive shaft or rear end. The service writer called the service manager and he right away said he has seen this before and it ended up being the ring and pinion gears. We went for a test drive and he felt it and was sure it was in the rear since it only happened when the power was unloaded.

They stated the pinion preload was excessive and the backlash was out of spec. They replaced the ring and pinion, carrier bearings and pinion seal. After three days, Friday through Monday, since they had to order parts. It rides great now, no more vibration. I couldn't believe the difference since it's been going on for so long.

 

Excellent good story!

 

Glad you got it fixed! Unfortunately, they did the same to mine but it made no difference.

 

Darn. First time I read about a MaxTow having a (9.75) differential issue. Guess it's not immune. Oh well. Hey, do you have the E-locker or not? Would it make any difference on this issue? Mine has it. Oh, and at how many miles did you first notice it? Curious about that. Thx.

 

I have a similar issue... but the vibration only lasts a few minutes. I was told by the dealer, under certain conditions, even if the transfer case was in 2WD... the truck will engage the front diff as a method of warming the gear oil. After a few miles, I don’t feel the vibration.

Has anyone else heard of this?

 

Yes it was explained in a thread here not long ago. I cannot recall which it was but you could try a search. Maybe a call to customer service too to confirm (you know the internet). Either way there still should not be a vibration. It usually means something is amiss.

 

I have the locker and that shouldn't make any difference. The vibration started at around 8 or 9K, I only have 15K on it now. It was slow to come and only got worse over time. It was more annoying than anything else since that's the speeds I drive all the time. Once I realized it was happening I was more aware of it. It doesn't sound like it was specific to the 9.75 since all the work done eludes to a bad initial setup

 

Glad it worked out for you. I have a vibration that I'm confident is inside the rear end. It feels like the gears dont mesh properly. It's a "dull" vibration that resonates through your ***. Been to 3 different dealers and they all "cant replicate" or "that's the way the truck feels." I think these guys have a preconceived idea of what they're looking for, and if they don't feel it, it doesnt exist. I try to describe it as best I can, but no luck. When they hear vibration, they're looking/feeling for balance issues. I asked the last guy to crack the rear end open, and he said no. I'm considering putting up the book rate for someone to open the rear, just to get it fixed.

 

IIRC, that "feature" is on the 2017 model year up. The truck engages the IWEs, not the Transfer Case.
Here is the writeup for 2019.
2019 F-150 - 4WD - Revised IWE Operation Strategy After Initial ***SSM 48088*** - Ford F150 Forum - Community of Ford Truck Fans

 

I had the vibration too during coasting at 80km / hr. Tried many things.... ended up being the drive shaft. Now all fixed up. Hope that offers hope.