FINAL DRIVE GROUP 1141528 - Caterpillar

Illustration 1 g00729955
Components of the electronic control system for the transmissionThe electronic transmission control shifts the machine transmission. The shift is based on transmission speed and on the position of the shift lever (gear and direction).The electronic transmission control system consists of the following items.
Shift lever
ECM
Downshift switch
Neutralizer override switch
Neutralizer switch or two pressure switches
Auto/manual switch
Transmission speed sensor
Engine speed sensor
Transmission solenoidsThe control gets input from the switches and from the sensors. The control then processes this information and the control activates the appropriate transmission solenoids.The direction and the transmission gear are given to the control by the electronics of the shift lever.Note: The shift lever should be in the neutral position when the key is turned to ON. If the shift lever is not in the neutral position, the shift lever must be returned to the neutral position before a direction can be selected.Two systems of transmission neutralizing are used. Some models use a neutralizer switch that senses brake pedal travel. The 924 and 928 use a system of two pressure switches (80 psi and 220 psi) that sense brake pedal pressure.The neutralizer switch is actuated when the brake pedal is depressed. When the switch is actuated, the control will neutralize the transmission. When the transmission is neutralized, the transmission solenoids are not activated. The neutralizer switch of the brake pedal can be disabled by actuating the neutralizer override switch. When the neutralizer override switch is actuated, the lamp on the neutralizer is ON. The following operation is seen on 924 with pressure switches and the 928 with pressure switches. Upon detecting the 80 psi switch close, the transmission is neutralized by de-energizing the direction clutch only. The transmission remains neutralized until either the 80 psi switch opens or the 220 psi switch closes. If the 80 psi switch opens the transmission is placed back into gear. If the 220 psi switch closes the transmission remains neutralized until the 220 psi switch opens. At this point, the transmission is placed back in to gear.