Ok, I looked up your model and it is a direct drive washer made by whirlpool for sears.
If it does agitate it is not a bad motor coupler.
If the motor runs during spin the lid switch is ok, like you said.
This leaves us with only a few things. Being the motor coupler is good the motor should be turning the tranny in the spin cycle. If the tranny is not spinning the clutch then you have a bad tranny.
If the clutch is spinning it could be slipping, but it may smell then and still spin a little.
The other thing it could be is the drive block that connects the tub to the spin tube.
I would take a guess that maybe your trouble and it is easy to check.
Remove the agitator, there is a bolt in the top center that holds it on.
The top of the agitator will have a dispensor or cap that you will have to remove before you see the bolt.
Once you have the agitator removed put the washer in spin with the lid up so you can see what happens. You will have to push the lid switch in with a pen or something so the washer motor runs.
Looks close at the shaft, do you see anything turning?