Modifications or replacements of components within a vehicle's transmission system to enhance performance, durability, or efficiency. These upgrades can range from simple modifications like installing a shift kit or performance torque converter to more extensive overhauls involving stronger gears, upgraded clutches, or complete transmission replacements. The goal is to improve shifting speed, increase torque capacity, or optimize gear ratios for specific driving needs, such as racing, towing, or off-roading. Transmission upgrades are often sought by enthusiasts looking to improve the overall driving experience and performance of their vehicles.