587Fluid flow in second gear manual selection Figs 524 and 519

During this phase of gear change, the main pressure regulating valve and throttle pressure valve operate as for neutral and park.

When the manual selector valve is in '2' position, line pressure passes to the forward clutch piston to apply the clutch plates. Similarly, line pressure is also directed to the middle of the 1-2 shift valve. When road speed is high enough, governor pressure will be sufficient to push the valve to one side, thus uncovering the port feeding the accumulator and the second gear band servo piston on the applied side.

In the second gear — manual selection position, line pressure passing to the 2-3 shift valve is blocked so that a 2-3 upshift is prevented.

In first gear a reduced pressure is applied at the end of the main pressure regulating valve, causing a reduced line pressure to be created. Likewise in second gear full line pressure will act behind the main pressure regulating valve so that the line pressure is further reduced.

5.8.8 Fluid flow in drive range — second gear — forced kickdown (Figs 5.24 and 5.15(b)) Similarly as for all other manual selector positions, the main pressure regulating valve and throttle pressure valve operate in the same way as for neutral and park.

With the manual selector valve in D and the accelerator pedal fully depressed, the kickdown valve reduced waste aligns with the kickdown line outlet port thus causing throttle pressure to flow into the kickdown lines.

Kickdown pressure now flows to 1-2 and 2-3 governor plugs assisting the throttle pressure applied on the 1-2 and 2-3 shift valves. When the governor pressure is low enough, throttle pressure and kickdown pressure overcomes governor pressure, causing the 2-3 governor plug to move to the right. As a result, the 2-3 shift valve moves to exhaust oil from the drive and reverse clutch piston chamber and the second gear band servo piston spring chamber causing a 3-2 downshift to occur.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

Don't pay hundreds of dollars to find out what is wrong with your car. This book is dedicated to helping the do it yourself home and independent technician understand and use OBD-II technology to diagnose and repair their own vehicles.

Get My Free Ebook


Post a comment