The effectiveness of an individual part is dependent on the package they are included in:
- Street - Low increase of acceleration and top speed
- Pro - Moderate increase of acceleration and top speed
- Extreme - High increase of acceleration and top speed
- Unique - Increases stock acceleration and top speed without adding new parts
|Street||Differential||500||Available from the beginning of the game|
|Street||Lightweight Flywheel||400||Available from the beginning of the game|
|Street||Short Throw Shift Kit||100||Available from the beginning of the game|
|Pro||High Performance Clutch||1,000||Win 9 races during Stage 4 of the career mode|
|Pro||Limited Slip Differential||1,000||Win 9 races during Stage 4 of the career mode|
|Extreme||6 Speed Transmission||5,000||Find the Performance Shop in Coal Harbor West|
|Unique||-||-||Win 3 Outrun races during Stage 3 of the career mode|
- Differential - Limited Slip Differential - 6 Speed Transmission
- Transmission upgrades unlock final drive ratio adjustments, and can be used to adjust the ratio of all gears.
- 6 Speed Transmission upgrades are available for cars that already have them stock.
|Customisation in Need for Speed: Underground 2|