Vibration when towing

When towing boat with old tacoma there was no vibration.

with this newer tacoma I’m getting a vibration at 50+ higher mph Only when hauling boat. No vibration without boat. (Note- the rear tires have a very slight cup/uneven wear at edge of tire.). My thought the weight of boat is causing the uneven tire section to fully contactpavement causing vibration? Any helpplease?!

 

Your logic isn't bad. I would try to air down a bit so that you know for sure that the entire tire is touching the ground and put about the same weight as the trailer tongue weight in the back of the truck and see if it vibrates without the trailer being attached

 

I would be curious to see how your driveshaft angles change as you load up the rear of the truck .
https://www.tacomaworld.com/threads/just-fixed-driveline-vibration-for-free.153050/

https://www.tacomaworld.com/threads/the-tacoma-towing-bible.4031/