TRANSMISSION AR 3T4588 - Caterpillar

Illustration 1 g00333918
The shift lever switch selects desired speed and direction.
The transmission speed sensor measures the rpm of the transmission output shaft which relates to the ground speed.
The tractor transmission control regulates the shifting of gears. The tractor transmission control receives signals from the transmission hold switch, the speed sensor, the transmission switch and the shift lever switch. The transmission control responds to the signals by activating the upshift solenoid or the downshift solenoid.
When the transmission hold switch is activated the transmission hold switch prevents all automatic upshifts. When the transmission hold switch is in the test mode the transmission hold switch prevents all automatic upshifts. Automatic downshifts are inhibited unless the engine is in an underspeed condition. This condition exists in all forward speeds except one and eight. If engine speed decreases below approximately 1000 rpm, the transmission downshifts.
When the upshift solenoid or the downshift solenoid is activated, the solenoid delivers pressure oil to the rotary actuator. The action of the solenoids turns the rotary selector spool. This sequence selects the necessary pair of clutches that will be engaged for the next speed.
The transmission switch signals the transmission control. This signal indicates actual transmission gear that is engaged. The signal tells the transmission control when shifting is necessary.
The transmission hydraulic controls have four basic functions.
Fill time
Modulating time
Release time
Maximum pressureThe power train consists of three basic systems.
Transmission Control
Transmission and Torque Converter
Differential and Final DrivesThese systems are connected to each other in the following manner.
Hydraulically connected
Electrically connected
Magnetically connected
Mechanically connected
Illustration 2 g00334026
Tractor Power Train (1) Transfer gears (2) Drive shaft (3) Retarder (4) Engine (5) Torque converter (6) Transmission (7) Pinion gear (8) Differential (9) Final drive (10) WheelsThe tractor has eight speeds forward and one speed reverse. Transmission (6) is controlled by an electrical system and a hydraulic system. The selection of reverse, neutral and first speed forward is done manually. The transmission is an eight speed semiautomatic transmission.The flow of power is from engine (4) to retarder (3) , when the retarder is equipped. The power flows from the retarder through the drive shaft (2) and the transmission transfer gears (1) to the torque converter (5) . Power then goes to transmission (6) . In reverse, first speed forward, and second speed forward, the torque converter is in converter drive. In all other forward speeds, torque converter (5) is in direct drive. The power goes from the transmission through pinion gear (7) to differential (8) . Finally, the power goes through the axles and final drive (9) to wheels (10) .Retarder (3) is an option. When the machine is equipped with the retarder, a retarder control valve is needed. This requires different lines groups.