A/T System Description - Clutches

Transmission Cutaway View


NOTE: The illustration shows 4WD transmission on K20A4 and K20A5 engine models; 2WD does not have the transfer mechanism, K24A1 engine model is similar.

Idler Gears Section Cutway View 

Clutches


The 4-speed automatic transmission uses hydraulically-actuated clutches to engage or disengage the transmission gears. When hydraulic pressure is introduced into the clutch drum, the clutch piston moves. This presses the friction discs and steel plates together, locking them so they don't slip. Power is then transmitted through the engaged clutch pack to its hub-mounted gear. Likewise, when the hydraulic pressure is bled from the clutch pack, the piston releases the friction discs and steel plates, and they are free to slide past each other. This allows the gear to spin independently on its shaft, transmitting no power.

1st Clutch

The 1st clutch engages/disengages 1st gear, and is located at the middle of the secondary shaft. The 1st clutch is supplied hydraulic pressure by its ATF feed pipe within the secondary shaft.

2nd Clutch

The 2nd clutch engages/disengages 2nd gear, and is located at the end of the secondary shaft, opposite the end cover. The 2nd clutch is supplied hydraulic pressure by a circuit connected to the internal hydraulic circuit.

3rd Clutch

The 3rd clutch engages/disengages 3rd gear, and is located at the middle of the mainshaft. The 3rd clutch is joined back-to-back to the 4th clutch. The 3rd clutch is supplied hydraulic pressure by its ATF feed pipe within the mainshaft.

4th Clutch

The 4th clutch engasges/disengages 4th gear, as well as reverse gear, and is located at the middle of the mainshaft. The 4th clutch is joined back-to-back to the 3rd clutch. The 4th clutch is supplied hydraulic pressure by a circuit connected to the internal hydraulic circuit.

Gear operation

Gears on the mainshaft:
  • The 4th gear is engages/disengages with the mainshaft by the 4th clutch.
  • The 3rd gear is engages/disengages with the mainshaft by the 3rd clutch.
  • The reverse gear is engages/disengages with the mainshaft by the 4th clutch.
  • The idler gear is splined with the mainshaft, and rotates with the mainshaft.

Gears on the countershaft:
  • The final drive gear is integral with the countershaft.
  • The 1st, 2nd, 3rd, and park gears are splined with the countershaft, and rotates with the countershaft.
  • The 4th gear and reverse gear are rotate freely from the countershaft. The reverse selector engages 4th gear and reverse gear with the reverse selector hub. The reverse selector hub is splined to the countershaft so that the 4th gear and reverse gear engage with the countershaft.

Gears on the secondary shaft:
  • The 1st gear is engaged/disengages with the secondary shaft by the 1st clutch.
  • The 2nd gear is engaged/disengages with the secondary shaft by the 2nd clutch.
  • The idler gear is splined with the secondary shaft, and rotates with the secondary shaft.

The idler gear on the idler shaft transmits power between the mainshaft and the secondary shaft.
The reverse idler gear transmits power from the mainshaft reverse gear to the countershaft reverse gear, and changes rotation direction of the countershaft to reverse.

[P] Position

Hydraulic pressure is not applied to the clutches. Power is not transmitted to the countershaft. The countershaft is locked by the park pawl interlocking the park gear.

[N] Position

Engine power transmitted from the torque converter drives the mainshaft idler gear, the idler shaft idler gear, and the secondary shaft idler gear, but hydraulic pressure is not applied to the clutches. Power is not transmitted to the countershaft. In this position, the position of the reverse selector differs according to whether the shift lever shifted from [D] or [R] position:

  • When shifted from [D] position, the reverse selector engages with the countershaft 4th gear and the reverse selector hub, and the 4th gear engages with the countershaft.
  • When shifted from [R] position, the reverse selector engages with the countershaft reverse gear and the reverse selector hub, and the reverse gear engages with the countershaft.

NOTE: The illustration shows the 4WD transmission; 2WD does not have the transfer mechanism.