3. Gears are wheels with teeth that slot together. When one gear is turned the other one turns as well. If the gears are of different sizes, they can be used to increase the power of a turning force. The smaller wheel turns more quickly but with less force, while the bigger one turns more slowly with more force.
4. 4.10 gears are going to accelerate faster and decelerate faster on the lift. However, the trade-off is greater fuel consumption per mile driven and higher engine speed per given road speed. In basic terms, the 4.10 gears will feel quicker and 3.73 will feel faster.