AMC Coupes/Sedans/Wagons 1975-1988 Repair Information



The Laycock de Normanville overdrive unit for the Pacer is an electro-hydraulic actuated, planetary gear type, mounted to a special adapter at the rear of the transmission.

When the overdrive is in the direct drive position (overdrive switched off), and the car is driven forward, power from the transmission mainshaft is transmitted through the freewheel rollers and unidirectional clutch to the overdrive output shaft. When the car is backing up or during periods of engine braking, torque is transmitted through the clutch sliding member which is held by spring pressure against the tapered portion of the output shaft. When the overdrive is actuated, the clutch sliding member is pressed by hydraulic pressure against the brake disc (ring), which locks the sun wheel. As a result, the output shaft of the overdrive rotates at a higher speed than the mainshaft, thereby accomplishing a 30% reduction in engine speed in relation to vehicle speed.

The overdrive is actuated by a switch located beneath the steering wheel. This switch energizes a solenoid on the overdrive unit, via a switch on the transmission, which is cut in only when Third gear is engaged. The solenoid has two windings: a heavy control winding and a lower current, hold winding. When actuated, the control winding opens the overdrive control valve, whereupon the control winding is cut off and the valve is held in the open position by the hold winding. The control valve regulates the pressurized oil flow from the cam operated pump to the hydraulic pistons which operate the overdrive clutch sliding member.


See Figure 1

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Fig. Fig. 1: The overdrive unit is coupled to the transmission with an adapterPacer models

To facilitate removal, the vehicle should first be driven in Third gear with the overdrive engaged, and then coasted for a few seconds with the overdrive disengaged and the clutch pedal depressed.

  1. Remove the transmission from the vehicle as previously outlined in the Transmission removal and installation procedure in this section.
  3. Disconnect the solenoid cables.
  5. If the overdrive unit has not already been drained, remove the six bolts and the overdrive oil pan.

Be careful to avoid spilling hot transmission fluid on your skin.

  1. Remove the bolts which retain the overdrive unit to the transmission intermediate flange. Pull the unit straight to the rear until it clears the transmission mainshaft.

To install:
  1. Reverse the above procedure to install. Install the overdrive oil pan with a new gasket. After installation of the transmission and overdrive assembly, fill the transmission (which automatically fills the overdrive), to the proper level with the correct lubricant. Check the lubricant level in the transmission after driving 6-9 miles.