Seems like the center agitator is not is Not working and is loose. .

Use a 1/4 inch nut driver to tighten the set screw to the agitator shaft. It is about 3 inches up from the bottom of the agitator on the side of the agitator.

If this is a Whirlpool manufactured TOP LOADER, and this is a simple matter of the agitator not working, but everything else does, you may just have a worn agitator cam assembly, worn agitator dogs, loose agitator bolt, or all of the above. The following link explains what agitator dogs are and how to access them:

http://www.fixya.com/support/r3608577-replacing_agitator_dogs

Whirlpool manufactured washers use a split agitator design. The top half is known as the "auger, while the lower half is the agitator. Between the two pieces is a cam assembly, with small teflon teeth known as "dogs". There's also an agitator bolt that holds the entire assembly to the center post.

If the auger (top half of the agitator) is slipping, I would suspect the dogs or cam assembly need to be replaced. The part number for the dogs is included in the link I provided. For a little more you can purchase the entire cam assembly which includes the dogs, the cam, the cam seal and thrust bearing.

If the entire agitator appears loose or slipping, check the agitator bolt to ensure it is tight. DO NOT overtighten as this can restrict movement of the agitator or damage it. Tighten until snug.

Replacement parts (if required) can be purchased at any of the following websites:

searspartsdirect.com
pcappliancerepair.com
appliancepartspros.com
repairclinic.com

All these sites are reputable and offer great service with competitive pricing, so shop and compare. The first three sites I listed also include helpful exploded view parts diagrams to assist you in locating and properly identifying the parts you need. If you do not wish to order parts on line, use the part numbers from the Sears website and go to your nearest appliance parts retailer. All these parts are commonly sold as part of their in-store inventory.

If you have any questions, please post back and let me know. I hope this helps you.

you will need to remove your agitator. There should be a bolt on the top center of the agitator. you will need to remove the top of agitator or the cap to get to this bolt. once you loosen this bolt the hole agitator shold pull straight up.

Now you should see the long shaft in the center. Follow that shaft from the top down to the area where the shaft disappers and ther is a big round nut with 4 notches spaced evenly. This is call the spanner nut and you should use a spanner rench to tighten it with a small sleg or hammer ( a couple of good wacks should do. ) I know you probably do not have this tool, but at least you can verify that this is your problem. your spanner nut may be loose. this nut holds your inner tub down to the block. here is the break down

It is probably reverse thread, so you are probably turning the wrong direction.

This problem is usually attributed to either a loose agitator bolt, or the agitator dogs wearing out. The following link explains:

http://www.fixya.com/support/r823955-replacing_agitator_dogs

The upper portion of the agitator is called the "auger". If it is loose, simply tighten the bolt under the center post cap. DO NOT overtighten as this can cause damage to the agitator, or restrict motion. Just tighten until snug. If you have questions along the way, please let me know. I hope this helps you.

Look at the center. can you pull the agitator up and out of the tub? You can try it with the motor running but don't grab it too snugly. Try and push it up and down while running. If it seems to try and move there used to be a rubber spindle on the trans shaft under the agitator that would become separated. I don't know if yours has one or not but the agitators were a bugger to remove usually because of the corrosion that happens. A special tool that was an air bladder used to fit under the agitator and you'd blow it up like and inner tube and pop it off. If you get the agitator off you try to get it to agitate and if you cant stop it by hand your at the problem either you'll see it obviously or it will come apart inside the agitator.

Pop the top cover on the agitator.
Remove the screw inside.
Remove the agitator and inspect it for damage where it attaches to the transmission shaft.

Check and see if it spins freely in both directions. If it does, this means that your "dogs" are worn out in the top agitator. This is an easy fix. You just get the new ones (usually 10$ or less), pull the top cover off the agitator, then pull the center cap off inside of the agitator. Then you just remove the center bolt and pull the whole top agitator off. You will see the 4 plastic dogs right on the top of the agitator.

Just reach down between the basket and the agitator, and lift really hard straight up. Be sure not to hit yourself in the head when it pops loose. GE agitators just snap on to the air-bell underneith. Be sure that bell isnt loose after you remove. Good Luck!!!!

Look toward the bottom end of the agitator. There should be a small indentation where a 10mm screw is. This screw holds the agitator the the transmission shaft. Sometimes the screw works loose and needs to be tightened.