Q:

What test can I do to my washer's gearbox to determine whether or not it is bad?

I have a Kenmore washing machine (model 110.92273100) that doesn't spin.  I've taken the gearbox off, and when I spin the input shaft (motor coupler), it seems to act the way I would expect.  When I spin the input shaft one way, the outer output shaft (which attaches to the drum) spins.  When I spin the input shaft the other way, the agitator shaft slowly spins back and forth.  However, I can hold the output shafts still with my hand, and continue to spin the input shaft.  
Does the fact that I can spin the input shaft while holding the output shaft still mean that my gearbox is bad and needs to be replaced, or is it supposed to do that?
Is there a different test that can be done to determine whether or not my gearbox needs to be replaced?

A:

I decided to go ahead and buy a replacement gearbox.  Testing the new gearbox before I installed it, I determined that the answer to my question is yes, my test does mean that the gearbox is bad.  With the new gearbox, I was not able to spin the input shaft and hold the output shaft still at the same time.
I installed the new gearbox, and now the washer works again.

A:

After a bit of research it turns out that washing machine gearboxes are quite the complicated beast and have vastly varying designs. Without knowledge of the internal workings, it's hard to say if this is normal behavior.
Other methods for determining if a gearbox is bad include:

Checking for excessive play on the input and output shafts, which would indicate a bad bearing.
Listening/feeling for rough rotation or a grinding sound while rotating by hand.

Alternatively, the source of the problem could be a different component entirely.
Repair Clinic lists several reasons why your model of washer won't spin. The top four reasons were:

Bad lid switch assembly
Broken motor coupling
Worn or loose drive block
Worn clutch assembly 

Disclaimer: I have no affiliation with www.repairclinic.com

