EE reports was assisting install a tail (bin) pulley out of a manlift along with a second employee. The second employee was using a come-along to lift the pulley up so they could get it in position when the EE decided to assist by pushing the pulley. It weighs approx. 100-150 lbs. As the EE began to push, EE felt pain in lower back. EE started PT on 11/14/2024.