Amana ALW780QAW mold in agitator

Make sure the washer is level, especially front to back. Do not overload washer. Check to see if marks are coming from build up of gunk in the outer bowl.

The agitator and s/s bowl needs to be removed for cleaning.
You need to use a pressure washer to remove buildup on s/steel bowl
The bucket aka tub needs to be cleaned also check for items that may block or jam pump at the bottom of the bucket.
reassemble your machine, it should do a better cleaner wash.

Check and see if there is a cup in the top of the agitator. Some machines have you put it there, turning back and forth during wash doesn't bother it, but the spin to empty the wash water causes the softener to go out through slots in the top of the cup and be held in the agitator. when it stops the softener drains into the tub, ready for the rinse cycle.

Usually problems like this, you just have to take it apart and see. I can tell you a few things that will help though. It's not a deteriorating belt. In fact this machine doesn't have a belt at all, it's what is called "direct drive". The closest thing it has to a belt is a round piece of rubber in between a gear but that's near the motor and it's not possible for it to get inside the tub. In fact, it's hard for anything to get in there to stain clothes. Usually what causes this, is a build up of dirt, soap, mud, mold, etc that collects under the agitator and finally just gets enough to start releasing into the tub. It's pretty easy to take out the agitator and check under there, here's how.

To remove the agitator on a Whirlpool top-load washer, remove the solid cap or fabric softener dispense from the middle of the agitator. Then remove the white cap on the inside of the agitator. This might be stubborn, so just start off pulling gently and keep pulling until it comes out. Under that is a 7/16" bolt. Remove that and then the agitator will slide off the transmission shaft.

The only other option is removing the inner tub entirely, but that requires a special tool to get a nut off of the drive block, so that limits DIY repairs.

Unplug the Amana washing machine from the wall outlet, and open the lid. Pull the liquid fabric softener dispenser straight off of the top of the agitator. Some Maytag washers require the use of a flat head screwdriver inserted between the dispenser and the top of the agitator. Twist the handle of the screwdriver to pop the dispenser off of the agitator.

Remove the barrier cap inside the agitator using your hands. Pull the barrier cap straight out of the agitator. There is an O-ring that attaches to the outside of the barrier cap. If it did not come out with the cap, pull the O-ring out of the center of the agitator.

Remove the bolt securing the agitator to the drive bell with the socket wrench. The bolt is inside the center of the agitator.

Place your fingers in between the bottom of the agitator and the tub. Lift straight up to remove the agitator from the tub. Keep your head out of the way in case the agitator is stuck and unexpectedly releases. If necessary, use agitator hooks. Insert them under the agitator and push down on the hooks to release the agitator.

I have this same model and although I'm not sure what your problem could be, I do know how to remove the agitator. Get a new repair guy because you just pull up on the agitator to remove it. It is just pressed onto a cogged drive at the bottom. I read on the Internet somewhere that if you do lots of heavy loads, the agitator can slip on the metal cogged drive. So I would suggest that you pull straight up on the agitator and clean off the cogged drive and inspect the underside of the agitator to see if the corresponding grooves are worn down from slipping. You might run a cycle with the agitator out and see if the cogged drive is turning.
HTH

the fabric softener spins out of the cup after the wash cycle when spinning the water out of clothes, then the washer fills back up for the rinse w/ your softener having been dispensed. is there a nut at the bottom of your agitator where you see the gunk? If so you can take the agitator out by removing the nut but be careful of the little parts that make the agitator agitate. Do not disturb these little parts if you don't know about them. Does the gunk smell like grease or a mechanics garage? If so chances are it is a lubricant and should not be removed replace the cap and your softener cup and continue enjoying your machine.

remove fabric softner cup from top of agitator and remove 1/2 bolt for inside agitator then you'll need spanner wrench to remove nut that hold spin basket in tub. maybe use some affresh tabs or washer magic to remove build up

The build up is always going to be there as long as your using softener.The way to beat this is 1.add the softener directly into the tub before last rinse.2.Dillute it with water.3.Stop using softener and this cant ever occur./// The fabric softeners brand may make a difference,try another brand .If its watered down its less sticky.

Without knowing the age of your machine, your agitator "dogs" may be wearing or worn out. It should be fairly easy to check them out. You will need to figure out how to remove the agitator Usually the agitator will have a fabric softener dispenser or a cap on the top. Pull the dispenser/cap off the top of the agitator and you may see a screw holding the agitator in place. Once you lift the agitator out, the "dogs" should be visible. Most appliance stores should carry the dogs for your particular washing machine. I've added a couple of photos so you have an idea what to look for.

Black powder under the motor??? The motor uses carbon "brushes" to electrically make the motor move. Without going into motor theory, I would tell you that the black powder, in a small amount, is normal. The brushes can be replaced, and again, can be found at most major appliance dealers