Vibration at 50-65mph

just looking for ideas on this as something like this is hard to diagnose...

here's what's going on:

Vehicle is 2018 dclb trd sport with 10500 miles. Issue started art approx 9000 miles. No mods...original tires.

1. Slight harmonic vibration coming from middle to back of truck from 50-65mph. Can be felt in floorboard and heard
2. Occurs when accelerating or decelerating
3. Occurs regardless of what gear transmission is in
4. Occurs in 2wd or 4wd
5. Dealer balanced wheels at 10k service. No noticeable difference

Anyway, just looking for some thoughts on things to look for as I suspect that I'm headed down the "can't duplicate" road with the dwalership

 

Try to rotate tires front to back. If vibration shifts to steering then it’s the tires.

 

If it happens at 50MPH-65MPH under the conditions you stated I don’t see how it can’t be duplicated, unless I’m missing something. It’s under warranty though, use it. I’d ride along with whoever the dealer sends out to point out the things you notice. If you haven’t modded the truck I would say it’s strictly the dealers issue and not yours as you are driving the truck as it designed/engineered.

 

This vibration is not so bad that it shakes and shimmies the vehicle, it's absolutely there though. My 2016 tacoma had the dreaded rearend whine that I had several people ask me what that noise was and when I took it to the dealer they said they couldn't hear it??

I plan on working with the dealer on this, just curious if others may have had something similar and what they found that fixed it