Washing Machine is BangingFirst make sure Tiddles the cat is still on the outside and wasn't sleeping in the laundry basket. If so check that the load has not become unbalanced. This occurs more often with a small load rather than a heavy load. As the washer is spinning, the clothes become unevenly distributed meaning one side is heavier than the other. This causes the drum to wobble when spinning.
If the banging is constant for different loads, then the cause could be one of the following, most of which are not easily repaired.
Drum BearingsBearing problems normally cause rumbling noises as the drum spins which gradually get louder. The bearing are located between the inner drum and the outer case. Repairing these is very involved and requires removing and stripping the drum.
SuspensionThere are two types of suspension commonly found in washing machines.
Shock absorder types can break their legs or lose oil in the dampers. In this case this must be replaced.
The spring and friction plate type can lose its grip when the plate becomes shiny. Sometime you can just sand these down to restore the grip, otherwise they will need to be replaced.
Something LooseCheck that there is nothing loose around the drum that is vibrating and banging as it spins. A visual inspection should be enough to identify any loose bolts, or items hanging away from their mountings.
Unregulated MotorWhen the machine starts its spin cycle, it must build up the speed gradually. This is to make sure that the load is evenly distributed once it goes into the full spin. If not the load will tend to form in one place and create an unbalanced load.
This is generally controlled by a module on the main board that will need calibrating or replacing.