I'm not sure about LG Tromm, but on most other brands, when the dryer is stacked on the washer the dryer legs are either removed or turned all the way up. There are then brackets that attach the dryer to the washer, or tabs on one or the other that fit into slots on the other. Once the tabs are in their corresponding slots, screws are inserted that lock the dryer in place, turning the stacked pair into what is essentially a single unit. Hence, only the washer feet are used in leveling. Incidently, when leveling your machines, don't place the level on the top, place it vertically along one side, then vertically along the front of the machines. When your spirit level indicates you're level in both directions -- then the machines are properly leveled. Hope this helps. James

I too have a rattling LG dryer. I thought it was the metal gas hose connection rattling in back but established today it is the bottom panel of the the dryer unit. If I place my hand under the front of the unit and press up, the rattle stops. Moving the dryer to different postions, I noticed that the rattle goes away when the dryer is moved to a particular spot, which must be just the right spot that levels this ultra touchy unit. So my issue is the leveling, not internal parts. Now the challenge is to get the feet to the exact right adjustment so it doesn't ratttle when the dryer is slid back to where it belongs. Because I can't adjust the back feet in that position, the task is going to be annoyingly difficult. The dryer sits on tile which may make the rattle more likely. I have the same dryer at a vacation home which sits on luxury plank vinyl and it has never rattled.

The washer should be level first. Then when you stack the dryer on top, it's feet can all be the same height depending on the stack kit. I know, leveling a washer can be tough. Especially when you have such a tight space. It's hit or miss. Keep trying until you get it even as possible. Also, make sure the washer is solid. Try rocking it from corner to diagonal corner...each direction. If one direction has more wiggle, then slightly extend the leg involved. A quarter turn is all you may need. That being said, I really don't know how much vibration is normal. I'm in the same boat with my front load unit. I'd say, yes, your vibration is normal. I'd say, if the spin is ok, then it's ok.

Leveling is not so crucial as ensuring that the machine is evenly supported on all four corners. There's no way to 100% avoid all vibration. Many washer tub assemblies oscillate more at a specific speed range during spin acceleration, then settle down when that speed is passed as acceleration continues. Some machines have a sensor that detects excess oscillation and moderates the speed to keep it either or above or below that point ... which takes a few seconds to accomplish ... 30 seconds is not unreasonable. Some also have a gyroscopic balance ring integral to the drum, containing water or other fluid and some also contain free-floating ball bearings that position opposite the heavier part of the spinning load to offset it.