Clutches

Clutches

The four-speed automatic transmission uses hydraulically actuated clutches to engage or disengage the transmission gears. When clutch pressure is introduced into the clutch drum, the clutch piston is applied. This presses the friction discs and steel plates together, locking them and preventing slip. Power is then transmitted through the engaged clutch pack to its hub-mounted gear. Likewise, when clutch pressure is released from the clutch pack, the piston releases the friction discs and steel plates, and they are free to slide past each other whilst disengaged. This allows the gear to spin independently of its shaft, transmitting no power.

1st Clutch

The 1st clutch engages/disengages 1st gear, and is located in the centre of the secondary shaft. The 1st clutch is located in front of the 2nd clutch. Clutch application is by hydraulic pressure, oil being supplied via the feed pipe in the secondary shaft.

1st-hold Clutch

The 1st-hold clutch engages/disengages 1st-hold or 1 position, and is located at the end of the countershaft, just behind the torque converter housing. Clutch application is by hydraulic pressure, oil being supplied via the feed pipe in the countershaft.

2nd Clutch

The 2nd clutch engages/disengages 2nd gear, and is located in the centre of the secondary shaft. The 2nd clutch is located behind 1st clutch. Clutch application is by hydraulic pressure, oil being supplied through the secondary shaft from the internal hydraulic circuit.

3rd Clutch

The 3rd clutch engages/disengages 3rd gear, and is located in the centre of the mainshaft. The 3rd clutch is located in front of the 4th clutch. Clutch application is by hydraulic pressure, oil being supplied through the mainshaft from a circuit connected to the regulator valve body.

4th Clutch

The 4th clutch engages/disengages 4th gear, and reverse gear, and is located in the centre of the mainshaft behind the 3rd clutch. Clutch application is by hydraulic pressure, oil being supplied via the feed pipe in the mainshaft.

One-way Clutch

The one-way, clutch is positioned between the countershaft 1st and 3rd gears, with the 3rd gear splined to the countershaft. The 1st gear provides the outer race surface, and the 3rd gear provides the inner race surface. The one-way clutch locks up when power is transmitted from the mainshaft 1st gear to the countershaft 1st gear. The 1st clutch and gears remain engaged in the 1st, 2nd, 3rd and 4th gear ranges in the D4, D3 or 2 positions. However, the one-way clutch disengages when the 2nd, 3rd or 4th clutches/gears are applied in these positions. This is because the increased rotational speed of the gears on the countershaft overrides the locking "speed range" of the one-way clutch. Thereafter, the one-way clutch freewheels with the 1st clutch still engaged.