If the contents of the drum check out okay then a bad drum support roller could be causing a thumping noise.
Dryer vibration on floor.
My again non physics expert mind s theory is that this spreads the vibration load out to more planes points of contact.
There are several ways you can complete this task in a short time for little money.
If a stackable washer dryer unit is vibrating it may not be level.
Noise from the dryer often means that a hard object is clanging around inside the drum the zipper on a sweatshirt change left in a pocket your phone.
Step 1 check if it s level.
Multiple issues can cause a dryer to vibrate and make a lot of noise from an overloaded dryer to a defective component.
I haven t tried this yet.
If the laundry appliances are on the main floor and adding bracing in the ceiling of the level directly under the washer is possible this should give the washer a sturdier stable floor and minimize vibrations.
If it s not possible to add bracing as described you can place a 5 8 or 1 inch sheet of plywood under.
A damaged idler pulley idler pulley bracket or idler pulley tension spring could.