Function (page 2 of 2)

There are in fact, two springs inside the valve. The largest spring has a low spring constant and is called low speed spring. The shorter spring (high speed spring), with a higher spring constant, is more influential upon the plunger. Therefore a higher primary speed is needed to balance the valve, for the same plunger displacement.

Depressing the throttle pedal completely, in the overdrive mode, will make the primary halves widen very quickly by bleeding primary pressure. If this should happen too fast, the pressure chamber in the secondary pulley cannot be filled fast enough, which could cause the belt to slip.

A sensor shoe on the primary pulley is mechanically linked with the secondary valve and an abutment on the spring of the primary valve. This abutment allows the spring force to increase and allows the transmission to up-shift, thus moving the abutment, allowing a higher spring force, etc.

As previously mentioned, the position of the throttle pedal also defines the spring force in the primary valve. This relationship is created by means of the ratio control motor.

The ratio control motor is connected to the main harness. The motor is operational in all transmission modes and adjusts the primary pulley to the appropriate position, via the hydraulic control unit.

Each primary speed is related, via the pitot pressure, with a specific force on the primary valve. This specific force must be compensated by the spring force.

As the vehicle speed increases, primary pitot pressure increases, overcoming spring pressure and secondary pressure can now flow through the valve into the primary chamber (primary pressure). If the throttle is depressed, this increases spring pressure, moving the piston, causing primary pressure to relieve to the sump, until the spring pressure is in balance with pitot pressure.