Why does the machine shake a lot on the spin cycle

How old is the machine? Does it do this every time or only when you are washing certain items. Fabrics like towels and blankets get Very heavy when wet so can cause a lot of shake in a machine.
This might also be an issue with the bearings on the drum. If the bearing is worn it can throw the machine out of balance as the drum isn't staying level as it spins. With the machine empty, open the door and turn the drum by hand. It should turn smoothly and have a small amount of swinging action forwards and backwards. If it feels 'gritty' as you turn it or the drum swings around a lot get a good repairer to look at it.

Washing machine leg leveling. I check mine seasonally.

Front Load Washer Vibration Level Legs

The machine must be level or it will shake. There should be feet under the front which screw in and out. Get a spirit level and adjust the feet so it is sitting level front to rear and side to side.
Also make sure it isn't rocking slightly when it's not running - if so screw out one of the feet till it's steady. If you don't have a spirit (bubble) level compare how vertical the sides are to the wall/cupboards etc. However a level is best as even a little lean can make it shudder.
Or your putting too much washing in it!

Hi

First check if the machine is level .Also makes sure you do not have an unbalanced load. Lint filter between the tubs is loose/broken, tub nut and drive block is worn, bad brake, worn spin tub are some various reasons when washer shakes in spin cycle.

Please check the bellow link to troubleshoot your problem:-

http://www.wikihow.com/Fix-a-Shaking-Washing-Machine

Please get back to us if you have further query else please accept the suggestion.

Thank you for contacting fixya.com

If front load check the inner drum If it is loose at all you have a lot of problem . Very expensive.

Machine legs should be adjusted so that machine is level and standing on all four legs. The load in the machine should be evenly distributed. Utube has an excellent video on washing machine repair.

you will have to re level the machine

The problem could an improper leveling of the machine.Also could be bad drum bearings or even damaged ones because of the previous heavy spins.

your suspension dampers is damaged on washing machine causing bad balance on spin cycle..

very loud in spin cycle can mean a bad rear bearing, not something a homeowner would want to try to replace, parts would exceed 6-7 hundered dollars. you may have some extended part warr through the manufacture. still probly gonna be a 5 hundred when the labor is added in