The CVT type automatic transmission utilises a metal drive belt and two pulleys, one primary and one secondary, that may assume variable diameters which give infinite gear ratios. It is controlled by a hydraulic system inside the gearbox. The engine power is transmitted to the gearbox via an electromagnetic clutch with engagement being controlled by an electronic switch linked to the accelerator.

The clutch gives gentle take up of drive in all conditions and excludes any form of drag when the car is stationary and the engine idling. High and low ratios are automatically selected by the gearbox in relation to engine speed, vehicle speed and load.

The CVT gear selector lever is similar to a conventional automatic transmission with only the following positions:

  • P = Park
  • R = Reverse
  • N = Neutral
  • D = Drive, for normal driving and
  • L = Low gear, for maximum engine braking and climbing steep inclines.

There are 3 safety interlocks on most CVT’   Transmissions.

  1. A mechanical interlock, which prevents the gear selector lever being moved until the push button on the   selector lever is pressed.
  2. An electronic interlock, which prevents the gear selector lever being moved from P (Park) until the ignition is turned on.
  3. A brake system interlock, which prevents the gear selector lever being moved from P (Park) until the foot brake pedal is depressed.

The ignition key can only be removed from the stop/off position when the gear selector lever is in the P (park) position.

In an emergency the gear selector lever can be manually released by inserting the ignition key in a special slot next to the gear lever. Also in an emergency the ignition key can be removed when the gear selector is NOT in P (park) by pressing a release device under the steering column.

Most CVT’s are fitted with an audible alarm, which sounds under the following conditions:

  1. When the gear selector lever is moved to R (Reverse)
  2. When the ignition key is turned to stop/off when the gear selector is NOT in P (park)
  3. When the drivers door is opened with the ignition key NOT in the stop /off position and the gear selector lever NOT on P (park).

Driving a vehicle fitted with a CVT is very similar to most vehicles fitted with a conventional hydraulic automatic transmission except there is no “creep”.

When the engine is idling with the gear selector lever in D or L, the clutch automatically disconnects the drive. Providing the accelerator is not touched and the engine is idling the driver has to apply the foot brake for short stops at traffic lights.

For longer stationary periods the hand/parking brake must be applied. On gradients DO NOT press the accelerator to keep the car stationary, use the foot brake or parking brake as the vehicle will roll.

On some later CVT’s, some vehicle manufacturers e.g. Ford, have built in “creep” so that the transmission behaviour is similar to a conventional hydraulic automatic gearbox.

Another unusual feature of vehicles fitted with a CVT is that they appear to rev more freely and to new users will seem to be over revving. This is normal, and is because the CVT has a seamless drive and changes in gear ratio (gear changes) are not detectable. The CVT will automatically select the correct ratio for vehicle speed, load and economy. The engine revs will decrease as a higher ratio is reached.  When “kickdown” is operated the engine revs climb quickly and the typical surge of power is not so marked.