What are the reasons for a diesel vehicle not being able to shift gears?

[Joseph]

The reasons for a diesel vehicle not being able to shift gears are as follows: 1. Common failure points for automatic transmissions that prevent gear shifting: Internal failure of the gear shift assembly leading to inability to shift gears. Failure of the control module inside the transmission. Failure of the gear position switch in the transmission. 2. Common failure points for manual transmissions that prevent gear shifting: Failure of the release bearing, friction disc, or pressure plate in the clutch system. Failure of the gear shift assembly. Failure of the gear shift mechanism. 3. Issues with the gear selection or shift cables: Manual transmission vehicles still use two cables for gear shifting during operation. If either of these cables breaks, it can lead to gear shifting problems. If it's a new car, the components inside the transmission may not have been properly run-in, making some gear parts stiff and resulting in difficulty shifting gears.