Spins, but doesn't agitate.

Our top load speed queen washer will spin like a champ, but doesn’t agitate. Based on the little bit of testing I have done I can get it to agitate when I manually pull the belt the opposite direction that the motor spins while in the spin cycle. How do I test to see if the motor is the problem or if the timer is not sending the voltage to tell the motor to spin the the correct direction to agitate? I’m guessing that the timer sends voltage during the spin cycle to spin in one direction and then during the agitation cycle to have the motor spin in the opposite direction. Or is there a secondary switch that tells the motor to go the opposite direction? Thanks for the help.