* Transmission fluid is low or dirty. Check the transmission fluid level and condition. If the fluid is low, add the recommended fluid type and check for leaks. If the fluid is dirty, it should be replaced.
* Shift linkage is loose or damaged. The shift linkage connects the gearshift lever to the transmission. If it is loose or damaged, it can prevent the gears from engaging properly. Inspect the shift linkage for damage and adjust or repair as necessary.
* Clutch is not fully disengaging. The clutch disengages the engine from the transmission when you shift gears. If the clutch is not fully disengaging, it can prevent the gears from engaging properly. Check the clutch fluid level and condition. If the fluid is low, add the recommended fluid type and check for leaks. If the fluid is dirty, it should be replaced.
* Synchros are worn or damaged. The synchronizers help to align the gears so that they can engage smoothly. If they are worn or damaged, they can prevent the gears from engaging properly. Synchronizers can be replaced, but it is a major repair.
* Gearshift forks are bent or damaged. The gearshift forks move the gears into place when you shift gears. If they are bent or damaged, they can prevent the gears from engaging properly. Gearshift forks can be replaced, but it is a major repair.
* Transmission is damaged. If the transmission is damaged, it will need to be repaired or replaced. This is a major repair.
