• Shifting gears
  
  

The Facts

• A manual transmission (not to be confused with a manual transaxle, which performs the same function for front wheel drive vehicles) changes the amount of torque that is transmitted from the engine to the drive train. The transmission achieves this through the use of a series of gears, synchronizers (which allow the gears to mesh), shift forks and shift linkage. The operation of these parts is controlled via a gear shift lever, which is operated by the driver. By changing the gears, the driver can change the speed and torque of the vehicle's drive wheels as related to the engine's speed and torque.
  
  

Grinding Gears When Shifting

• Clashing of the gears while shifting can be caused by an incorrect adjustment of the transmission linkage. A worn linkage can cause the gears to not engage properly. A dragging clutch can cause the teeth of the synchronizers to grind, especially as the transmission is being shifted out of neutral. Other causes of grinding gears include excessive wear or damage to synchronizers or shift forks.
  
  

Transmission Noise

• If the transmission is making a roaring, humming or whirring noise, the transmission lubricant (oil) may be low.
  
  

Difficulty Shifting

• If the gear shift lever is difficult to move through the gears, the problem might lie in the linkage or shift mechanisms. Sometimes a bent or badly aligned shift rod can result in hard shifting. Another cause of hard shifting is related to the clutch linkage, which may not be releasing the clutch completely.
  
  

Transmission "Pops" Out of Gear

• When the transmission spontaneously jumps out of gear while the car is in motion and the gear shift lever moves to neutral, it may indicate a bad shifter assembly or a worn clutch pilot bearing. Other problems that may cause the transmission to jump out of gear include an excessive amount of play in the countershaft and output shaft assemblies, excessive wear to the shift fork assembly or shift rails and worn synchronizer springs and inserts.
  
  

Leaking Transmission Lubticant

• Manual transmission oil leaks are typically caused by ruptured gaskets, seals that have become worn, loosened fasteners or by damage to the case or housing.
  
  

Transmission Stuck in One Gear

• A bent shift rod, worn linkage or worn shifter arms may cause a manual transmission to become locked in one gear. Another possible source of this problem might be broken drive gear teeth. Sometimes the teeth jam together and become locked up from bits of metal that have chipped off the teeth.