If the level is correct: Check the shift actuator on the side of the shift lever housing.
Check that there are no foreign objects in the gear shift actuator (from the side of the gear lever housing and from the side of the gearbox), interfering with his work.
If necessary, set the tie rod correctly.
Check that the shift cable is not broken or jammed and is properly connected to the gearbox and to the shift lever housing. Check adjustment.
If a problem is found, repair the shift cable or reattach it correctly.
If the cable is damaged, replace the shift lever housing. Make sure the shift lever housing is securely fastened. If necessary, secure the shift lever housing.
If the operation is not possible, replace the shift lever housing.
If the shift actuator on the shift lever housing side is OK:
- turn on the transmission;
- put the car on a lift;
- block the right front wheel with a screwdriver;
- try to turn the left front wheel;
- repeat the test with the left front wheel blocked.
If the unlocked wheel spins without turning the entire wheel drive shaft, replace the defective wheel drive shaft.
If the unlocked wheel spins, turning the entire wheel drive shaft, replace the manual transmission.
If the front wheel drive shafts are in good order, make sure that the clutch disc has not collapsed under the action of centrifugal forces by looking through the mounting hole for the starter to see if there are pieces of friction linings of the clutch disc on the clutch housing. Replace the clutch kit if necessary.
If the clutch is correct, place the shift lever in neutral:
- remove the rear cover of the gearbox housing;
- check the alignment of the shift forks;
- make sure there are no jammed gears.
Unlock jammed gears.
Remove the manual transmission.
Check that two gears are not engaged at the same time, and the gear selector is not stuck in the synchronizer clutches.
If necessary, unlock the transmission and replace the shift control mechanism (forks, shift shaft, clamps).
In all other cases, replace the gearbox.