This document summarizes a study on hard shifting of gears and abnormal noise from the transmission box of four-wheeler vehicles under varying loads and speeds. The study found that hard shifting and a "kat-kat" noise were caused by worn synchronizer rings in the transmission. Replacing the synchronizer rings resolved the issues. Improper driving techniques like shifting gears at inappropriate times can accelerate wear and lead to transmission problems. Maintaining vehicles properly and avoiding water contact with the gear box can extend the life of the transmission components.