Engine/Transmission Relations

   An important part of transmission diagnosis is to make certain the engine operates properly. If the engine performance is incorrect, the transmission will receive the wrong information. Many times what is perceived as a transmission problem is in actuality an engine problem. So before you make any attempt to diagnose a transmission problem, be sure engine systems are operating properly.

   Keep in mind that this article deals with automatic transmissions in general. You should always check the proper service and repair manual for your vehicle for specific information.

There are two basic types of automatic transmission

The transmission is a device that is connected to the back of the engine and sends the power from the engine to the drive wheels.  An automobile engine runs at its best at a certain RPM (Revolutions Per Minute) range and it is the transmission's job to make sure that the power is delivered to the wheels while keeping the engine within that range.  It does this through various gear combinations. In first gear, the engine turns much faster in relation to the drive wheels, while in high gear the engine is loafing even though the car may be going in excess of 70 MPH.  In addition to the various forward gears, a transmission also has a neutral position which disconnects the engine from the drive wheels, and reverse, which causes the drive wheels to turn in the opposite direction allowing you to back up.  Finally, there is the Park position.  In this position, a latch mechanism (not unlike a deadbolt lock on a door) is inserted into a slot in the output shaft to lock the drive wheels and keep them from turning, thereby preventing the vehicle from rolling.