The agator is popping up - Kenmore 24872 Top Load Washer

This assumes that you have a basic Kenmore / Whirlpool top load, direct drive, neutral drain (it doesn't spin until the pump removes most of the water) machine.

First, see the Sears parts site for your washer:

http://www.searspartsdirect.com/partsdirect/index.action

Enter your model number (###.######) and you'll see a list of major sub-components with diagrams and parts.

It's possible that the plastic bolt that holds the agitator on the drive tube is loose or damaged.

Look at the section on the Sears site for Agitator, basket and tub.

Remove the fabric softener unit, lift the top agitator cap (use a screwdriver) and you should see a plastic part in the center of the top agitator with a 1/2" square drive.

If it's loose, use a 1/2 inch extension for a socket set to tighten it.

Also see the following illustrated description of how to get to it.

http://www.american-appliance.com/catalog/newsdesk_info.php?newsPath=16&newsdesk_id=136&osCsid=0da65cea0e338fe930b1fde153a243f0