Kenmore 80 series washer will not spin and I think I've tried it all....

My sister-in-law's washing machine will not spin. I can hear the pump come on and drain though. I spent a bit of time researching and watching repair videos on the common causes of this problem and assumed it must have been the coupler. I looked underneath, inspected it, and could see it was intact and rotating the drive shaft. I then dropped everything down and checked the clutch. Nope. The brake is firm and in good shape. I then separated the trans from the motor just to double check the coupler again. Still perfect. I have no idea what else to do.:help:

Kenmore 80 series washer will not spin and I think I've tried it all....