Take the cabinet off, bypass the lid switch and set it into a spin cycle. The motor should be running. At this point, watch the area above the transmission for the clutch plate to spin. If the clutch plate turns but no spin action is observed, the clutch is bad. If the clutch plate does not turn then the transmission is bad.
Usually you can get the tub to move by hand when it is running. If so this solidifies a bad clutch. A quick 30-minute repair. Only the agitator needs to be removed in order to drop the transmission, not the spin basket or anything else. No special tools, etc.