My washer pump is leaking and I plan to order a new one. How do I determine if a new pump-motor coupling is also needed?
Thanks,
Normally, I would just pull out the motor and check the coupling for wear. You might also find the pump rusted to the motor shaft. I usually pound it off with a hammer. When off, check the motor bushings for wear.
Good call.
If the motor shaft is rusted, you can grab the motor shaft with piers and move the pliers back and forth. That will break the rust off the motor shaft. Normally the pump comes off fine, though.
The coupler is probably OK. But, hey, if you already have the machine apart, it is not a bad time to replace it if you do not mind spending a few extra dollars. 
Matt