On high spin the drum bangs against the rear inside walls of the cabinet. Dents are noticable from where it violently shakes.

Most of the time a tumble dryer will work like a dream but, as with all appliances, occasionally there will be technical problems.
If your tumble dryer is making a banging, whining (or other strange noise) it's best to diagnose and sort out the problem. It could be the result of a number of things, but what you certainly don't want to do is ignore it.
Here are the most common reasons for your tumble dryer making odd noises.
Coins and keys
One of the most common reasons for a banging, rattling or clanking is keys or coins left in pockets - so always check them before you put any clothes in the tumble dryer. More often than not you won't hear anything until the dryer cycle is in full spin.
Uneven surfaces
If the dryer is vibrating or shaking during spinning, check to make sure the dryer's sitting on a level surface. If it's fitted with height adjusters on the front legs, adjust them accordingly to ensure the machine is level as this will often reduce or eliminate the banging sound.
Drum bearings
If the tumble dryer is noisy when its turning and the whole appliance is shaking and rumbling, it could be indicative of a problem with the drum bearings, which help the wheels turn freely and easily.
The drum
If the banging noise is continuous when the drum is turning then it might be problem with the drum itself. If the noise is a metallic one, it could be the result of the drum scraping on something inside the machine. You could always check the drum visually for any marks or dents.
Motor bearings
If the tumble dryer is emitting a high-pitched screaming or whining noise it could be a sign that the motor bearings are wearing out.
Tension pulley wheels
If there's a squeaking noise coming from the dryer it could be the result of wear on the tension pulley wheels. This occurs more frequently on older models...or try this link..
Common Tumble Dryer Problems

What is the complete model number of your unit?

In the rear

The clothes must be balanced inside the drum in order to stop the violent shaking. Unlike a front loader, the top loaders must be balanced before starting the load.

If you need more assistance, let me know.

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There are 2 shock absorbers/springs attached to the drum. If one of them breaks it will cause a loud banging noise when you wash heavy loads. This is an easy fix. The part is about $22.00 and it is accessed throught the front bottom panel.

I have a four year old Andi front loading machine, and just in the last week it has started to move violently during the spin cycle and move across the room.
The last time, the movement was so severe that the machine was cutting itself off and then trying to spin again.
I couldn't control the machine and I just had to turn it off at the wall.

investigated further by myself couldnt wait

slid the machine out away from the wall and tilt back enough to see underneath. just below the door there is a large concrete weight. chances are it is loose and needs to be tightened. if this problem has been going on for a while the bolts holding the weight on will have snaped and the drum/weight or both will need replacing . ( ex hoover engineer)

Remove top of machine and check the centralising springs are still attatched. If springs ok tilt machine against the wall after unplugging from the wall socket and check the shock absorbers. One of them could have jumped out of the guides. If shockies are ok, check the spider for cracks/breaks. The spider is the cast part that holds the outside drum in place. To check this you will have to remove the back plate.

Take the shipping bolts out from the back