CVT (Continuously Variable) Transmissions

Unlike other transmission types that use solid gears in one form or another to effect fixed gear ratios, CVT transmissions do not use any gears, except for a set of planetary gears and a couple of clutch packs to facilitate a reverse function.

How Does A CVT Transmission Work?

Instead of gears, CVT transmissions use two pulleys, the width of which can be adjusted in opposite, but equal amounts by actuators that are in their turn, controlled by microprocessors.

As a practical matter, one pulley is attached to the engine (typically via a torque converter to allow for a neutral stance), and another that is attached to the driving wheels via a conventional differential.

In terms of operation, “gear ratios” are established by varying the effective diameters of the two pulleys in opposite but equal amounts to maintain the proper belt of chain tension

For instance, when the vehicle pulls away from a standing start, the drive pulley will be set so that its effective diameter is smaller than that of the driven pulley.

While this reduces the rotational speed of the drive pulley at the point where the belt or chain runs within it, engine torque is multiplied proportionally by virtue of the difference in the drive and driven pulleys’ effective diameters

As the vehicle gathers speed, the effective diameters of the pulleys are adjusted continuously and seamlessly, which produces seamless acceleration

However, the adjustments to the pulleys are made in a manner that ensures that the engine is always running at not only its most economical, but also its most efficient speed for any given transmission “setting”.

In translation, this means that the engine may run at the same RPM’s over a wide range of vehicle road speeds, and that the effective diameters of the pulleys will only be changed when the engine is no longer running at its most economical and/or efficient speed

Advantages of CVT transmissions.

The two biggest advantages of CVT transmissions over other transmissions types are that when driven appropriately, a CVT transmission can produce fuel cost savings, and that its mechanical simplicity translates into a lower weight than other transmissions

Disadvantages of CVT transmissions

Disadvantages of CVT transmissions

Common symptoms of faulty CVT transmissions

Most common symptoms of defective, faulty, or malfunctioning CVT transmissions are much the same across all applications and can include the following...

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