Noise in the spin cycle

The noise was indeed coming from the water pump. To clean the pump on this top-loader you have to unplug it, pop the top open, and remove the front face of the cabinet to expose the motor and pump. Slip off the two metal clips hugging the pump to the motor. Place a towel under the motor before detaching the hoses - there's a plastic drip pan between the pump and motor to guide the water away from the motor. Unclamp the two hoses from the pump by squeezing their spring-clamps with pliers and sliding them further down the hose. Pull the hoses off by lifting the pump off its axle and pulling it out while wiggling the hoses loose. I found a small sock jammed in the pump - it must have fallen to the outside of the basket but inside the drum during the last spin cycle, and went down the drain hose. Check the pump for damage and replace if necessary. For future troubleshooting, remember that a clogged pump causes squealing, diminished spin speed, and slow drainage.