Why is maytag washer is making a loud bang sound at the end of the cycle?

My maytag washer approx. 2001, top load, oversize capacity, quiet pack, heavy duty with lifetime tub has just started making a loud "bang" as it finishes the wash or rinse cycle. It is still doing the job but I know it seems like only a matter of time before it stops???
Any idea as to what the problem may be?
(I've checked each time and it is not off balance...)

Thank you for any advise,

Laundry Girl