I just repaired a guys washer, clothes jammed under agitator caused the coupler to fail. I told him the coupler was designed to be a weak link in the event of something like this happening and he said that he read somewhere on this forum where an "expert" posted that in no way is the coupler designed to be a weak link and that you would never find that information in any Whirlpool documentation. Well, straight from the Whirlpool study course manuals, "The drive motor is connected to the gearcase through a rubber isolation coupling. This will compensate for any minor misalignment between the motor and the gearcase. In addition, the isolation coupling serves as a weak link between the gearcase and motor. Should the gearcase lock up, the isolation coupling and motor couplings will shear, which will prevent the motor from being damaged." Iv'e also seen similar wording in more than one Whirlpool service manual. Just for the record.
I was told by my washer repair man that the coupler is designed to fail in order to protect other components.
So instead of needing a new transmission or motor the rubber coupler or plastic part with three fingers (set of two) break instead.
It's relatively easy to replace and not expensive.