446B Backhoe Loader Transmission (Autoshift) Transmission Caterpillar

General Information

Illustration 1	g00831080
(1) Input shaft (2) Gear (3) Forward high clutch pack (4) Forward high clutch piston (5) Gear (6) Reverse clutch piston (7) Reverse clutch pack (8) Gear (9) Reverse shaft (10) Forward low clutch pack (11) Forward low clutch piston (12) Gear (13) Gear (14) Clutch pack for speed clutch 1 (15) Clutch piston for speed clutch 1 (16) Gear (17) Countershaft (18) Gear (19) Gear (20) Clutch pack for speed clutch 2 (21) Clutch piston for speed clutch 2 (22) Front output shaft (if equipped) (23) Clutch piston for the front output shaft (if equipped) (24) Clutch pack for the front output shaft (if equipped) (25) Gear (if equipped) (26) Gear (27) Gear (28) Rear output shaft (29) Clutch piston for speed clutch 3 (30) Clutch pack for speed clutch 3 (31) Gear (32) Gear (33) Gear

The transmission has the following features: five speed in forward, three-speed in reverse, constant mesh and countershaft transmission. The transmission contains electrical solenoids in order to shift from forward direction to the reverse direction. The transmission will shift from first through fifth gears. Fifth gear is automatically engaged from fourth gear when the ground speed reaches a set value.

The transmission has the following shafts: input shaft (1), reverse shaft (9), countershaft (17), rear output shaft (28) and front output shaft (22) .

The input shaft (1) contains the forward high clutch (3) and the forward low clutch (10). The reverse shaft (9) contains the reverse clutch (7). The countershaft (17) contains clutch 1. The rear output shaft (23) contains clutch 2 (20) and clutch 3 (30). The front output shaft (22) contains the clutch pack for the front output shaft (24) .

A speed clutch and a direction clutch must be engaged in order to send power through the transmission. The speed and direction of the machine must be selected manually by the operator. The operator uses the speed/direction control lever to select the speed and direction.

Illustration 2	g00685589
(1) Automatic mode (2) Manual mode

The autoshift switch is located on the right side of the dash on the machine. The control is used to select either manual shift (2) or automatic shift (1). The automatic mode allows the transmission to select a gear when the engine speed and the operating conditions are correct. When you are in the manual mode the transmission stays in the selected gear on the speed/direction control lever.

Table 1 gives the combination of the solenoids that are energized and the clutches that are engaged for each FORWARD speed and each REVERSE speed.

Illustration 3	g00807797
(34) Solenoid for speed clutch 2 (35) Solenoid for speed clutch 3 (36) Reverse solenoid (37) Forward low solenoid (38) Forward high solenoid

Illustration 4	g00807802
(39) Solenoid for the all wheel drive (40) Solenoid for speed clutch 1

The speed/direction control lever is a dual function lever. The gear selection is made by twisting the lever. The FORWARD selection is made by moving the lever up. The REVERSE selection is made by moving the lever down.

The operator changes the direction of the machine manually by rotating the speed/direction control lever. The transmission will automatically shift up to the highest speed that is selected on the speed/direction control lever when the autoshift mode is selected and the machine reaches a preset speed. When the autoshift mode is not selected, the transmission will engage the speed and direction that is selected on the speed/direction control lever.

The switches that are in the speed/direction control lever activate the electronic transmission control. The electronic transmission control executes the speed and the direction that is selected by the operator. The electronic transmission control energizes the solenoids for the transmission in order to engage the correct clutches for the direction and speed that is selected.

The electronic transmission control is located on the right side of the machine in the battery box.

The operator moves the speed/direction control lever in order to move the machine. The clutch engagement is done through an electrical harness that is connected to the electronic transmission control to the solenoids on the transmission.

The input shaft (1) sends the power from the torque converter turbine to the forward low clutch (20) and to the forward high clutch (30). The input shaft (1) rotates the same direction as the flywheel. Therefore, the plates also rotate the same direction at the same speed as the input shaft (1) .

The input shaft (1) contains two internal oil passages. The internal oil passages are for lubrication and cooling of the shuttle and for the engagement of the clutch packs.

FORWARD HIGH input gear (2) and FORWARD LOW input gear (12) are free to rotate on input shaft (1) when the clutch pack for FORWARD HIGH (3) or the clutch pack for FORWARD LOW (10) is not engaged. The discs rotate with the input gears.

Reverse shaft (9) and gears (5) and (8) provide reverse rotation to countershaft (17) when the reverse clutch (7) is engaged. Reverse gear (8) is meshed with gear (13). The power flows from the reverse gear (8) to gear (13) when reverse clutch pack (7) is engaged.

Countershaft (17) transfers power to the speed range gears on the rear output shaft (28). The speed range depends on the speed clutch that is engaged.

Illustration 5	g00848834
(3) Neutralizer switch

Illustration 6	g00848835
(4) Neutralizer switch (if equipped)

A neutralizer switch is located on the left side of the dash (3) and on the loader control lever (4). The neutral lock switch on the left side of the dash disables all transmission solenoids. The neutralizer switch that is located on the loader control lever disengages the solenoids for direction control.

If the machine is turned off, and the speed/direction control lever is left in the FORWARD position or the REVERSE position, the machine will not be able to start until the speed/direction control lever is returned to the NEUTRAL position.

The neutralizer switch (4) that is located on the loader control lever also is a downshift control when the autoshift function is selected. If the neutralizer switch is pressed and released within 0.5 seconds, the transmission will downshift to the next lower speed and an engine overspeed will not occur. The transmission can be downshifted multiple speeds if the button is pressed quickly multiple times.

Power Flow (First Speed Forward)

Illustration 7	g00808268
Power flow in first speed forward (1) Input shaft (2) Forward low clutch (3) Gear (4) Gear (5) Clutch pack for speed clutch 1 (6) Gear (7) Countershaft (8) Gear (9) Rear output shaft (10) Clutch piston for the front output shaft (11) Clutch pack for the front output shaft (12) Front output shaft (13) Gear (14) Gear

Illustration 8	g00807808
(15) Solenoid for speed clutch 1 (16) All wheel drive solenoid (17) Forward low solenoid

Torque from the engine is transferred through the torque converter to the input shaft (1). When the transmission is in FIRST SPEED FORWARD, the solenoid for forward low (17) directs oil to the forward low clutch (2) and the solenoid for speed clutch 1 (15) directs oil to the clutch pack for clutch 1 (5) .

When the forward low clutch (2) engages, power is transfered through the clutch to gear (3). Gear (3) transfers power to gear (4) on countershaft (7). When the clutch pack for speed clutch 1 (5) engages, power flows from gear (4) through the clutch pack to gear (6). Gear (8) transfers power from gear (6) to the rear output shaft (9) .

When the all wheel drive solenoid is energized, the all wheel drive solenoid (16) directs oil to the clutch pack for the front output shaft (11). Power is transfered from gear (14) on the output shaft (9) to gear (13) on the front front output shaft (12). When the clutch pack for the front output shaft (11) engages, the clutch pack transfers power to the front output shaft (12) .

Power Flow (Second Speed Forward)

Illustration 9	g00821767
Power flow in second speed forward (1) Input shaft (2) Gear (3) Forward high clutch pack (4) Clutch pack for speed clutch 1 (5) Gear (6) Countershaft (7) Gear (8) Rear output shaft (9) Clutch piston for the front output shaft (10) Clutch pack for the front output shaft (11) Front output shaft (12) Gear (13) Gear (14) Gear

Illustration 10	g00807811
(15) Solenoid for speed clutch 1 (16) Clutch solenoid for the all wheel drive

Illustration 11	g00807815
(17) Forward high clutch solenoid

Torque from the engine is transferred through the torque converter to the shaft (1). When the transmission is in SECOND SPEED FORWARD, the solenoid for forward high (17) directs oil to the forward high clutch (3) and the solenoid for speed clutch 1 (15) directs oil to the clutch pack for clutch 1 (4).

When the forward high clutch (3) engages, power flows through clutch (3) to gear (2). Gear (2) transfers power through gear (14) to countershaft (6). When the clutch pack for speed clutch 1 (4) engages, power flows through the clutch pack to gear (5). Gear (5) transfers power through gear (7) to the rear output shaft (8) .

When the all wheel drive solenoid is energized, the all wheel drive solenoid (16) directs oil to the clutch pack for the front output shaft (10). Power is transfered to gear (12) from the rear output shaft (8). When the clutch pack for the front output shaft (10) is engaged, the clutch pack transfers power from gear (12) to the front output shaft (11) .

Power Flow (Third Speed Forward)

Illustration 12	g00808276
Power flow in third speed forward (1) Input shaft (2) Forward low clutch (3) Gear (4) Gear (5) Clutch pack for speed clutch 2 (6) Countershaft (7) Gear (8) Rear output shaft (9) Clutch pack for front output shaft (10) Clutch piston for the front output shaft (11) Front output shaft (12) Gear (13) Gear (14) Gear

Illustration 13	g00807868
(15) Solenoid for speed clutch 2 (16) Forward low clutch solenoid

Illustration 14	g00807869
(17) All wheel drive solenoid

Torque from the engine is transferred through the torque converter to the input shaft (1). When the transmission is in THIRD SPEED FORWARD, the solenoid for forward low (16) directs oil to the forward low clutch (2) and the solenoid for speed clutch 2 (15) directs oil to the clutch pack for clutch 2 (5).

When the forward low clutch (2) engages, power flows through the clutch to gear (3). Gear (3) transfers power through gear (4) to the countershaft (6). When the clutch pack for speed clutch 2 (5) engages, power flows from gear (14) through the clutch pack to gear (13) on the rear output shaft (8).

When the all wheel drive solenoid is energized, the all wheel drive solenoid (17) directs oil to the clutch pack for the front output shaft (9). Gear (13) on the rear output shaft (8) transfers power to gear (12). When the clutch for the front output shaft (9) engages, the clutch transfers power from gear (12) through the clutch to the front output shaft (11) .

Power Flow (Fourth Speed Forward)

Illustration 15	g00808281
Power flow in fourth speed forward (1) Input shaft (2) Gear (3) Forward high clutch pack (4) Gear (5) Countershaft (6) Rear output shaft (7) Gear (8) Clutch pack for speed clutch 2 (9) Clutch pack for the front output shaft (10) Front output shaft (11) Gear (12) Gear (13) Gear

Illustration 16	g00807886
(14) Forward high clutch solenoid (15) Solenoid for speed clutch 2

Illustration 17	g00807888
(16) All wheel drive solenoid

Torque from the engine is transferred through the torque converter to the input shaft (1). When the transmission is in FOURTH SPEED FORWARD, the solenoid for forward high (14) directs oil to the forward high clutch (3) and the solenoid for speed clutch 2 (15) directs oil to the clutch pack for clutch 2 (8) .

When the forward high clutch (3) engages, power flows through the clutch to gear (2). Gear (2) transfers power through shaft (5) to gear (4). When the clutch pack for speed clutch 2 (8) engages, power flows from gear (4) through the clutch to the rear output shaft (6) .

When the all wheel drive solenoid is energized, the all wheel drive solenoid (16) directs oil to the clutch pack for the front output shaft (9). Gear (12) transfers power to gear (11) on the front output shaft (10). When the clutch for the front output shaft (9) engages, the clutch transfers power to the front output shaft (10) .

Power Flows (Fifth Speed Forward)

Illustration 18	g00808095
Power flow in fifth speed forward (1) Input shaft (2) Gear (3) Forward high clutch pack (4) Countershaft (5) Rear output shaft (6) Gear (7) Clutch pack for the front output shaft (8) Clutch piston for the front output shaft (9) Front output shaft (10) Gear (11) Clutch pack for speed clutch 3 (12) Gear (13) Gear (14) Gear (15) Gear

Illustration 19	g00807889
(16) Forward high clutch solenoid (17) Solenoid for speed clutch 3

Illustration 20	g00807890
(18) Speed sensor (19) All wheel drive solenoid

Torque from the engine is transferred through the torque converter to the input shaft (1). When the transmission is in FIFTH SPEED FORWARD, the solenoid for forward high (16) directs oil to the forward high clutch (3) and the solenoid for speed clutch 3 (17) directs oil to the clutch pack for clutch 3 (11).

When the forward high clutch (3) engages, the clutch transfers power from gear (2) through the clutch to countershaft (4). When the clutch pack for speed clutch 3 engages, gear (13) on countershaft (4) transfers power through the clutch to gear (12) on the rear output shaft (5).

When the all wheel drive solenoid is energized, the all wheel drive solenoid (19) directs oil to the clutch pack for the front output shaft (7). Power flows from rear output shaft (5) to gear (14). Gear (14) transfers power to gear (10) on the front output shaft (9). When the clutch for the front output shaft (7) engages, power flows from gear (10) through the clutch to the front output shaft (9) .

Power Flow (First Speed Reverse)

Illustration 21	g00808139
Power flow in first speed reverse (1) Input shaft (2) Gear (3) Reverse clutch piston (4) Reverse clutch pack (5) Gear (6) Gear (7) Gear (8) Clutch pack for speed clutch 1 (9) Piston for speed clutch 1 (10) Gear (11) Countershaft (12) Gear (13) Rear output shaft (14) Piston for the front output shaft (15) Clutch pack for the front output shaft (16) Front output shaft (17) Gear (18) Gear (19) Gear

Illustration 22	g00807919
(20) Reverse clutch solenoid

Illustration 23	g00807920
(21) Solenoid for speed clutch 1 (22) All wheel drive solenoid

Torque from the engine is transferred through the torque converter to the input shaft (1). When the transmission is in FIRST SPEED REVERSE, the solenoid for REVERSE (19) directs oil to the REVERSE clutch (4) and the solenoid for speed clutch 1 (21) directs oil to the clutch pack for clutch 1 (8) .

Gear (19) transfers power from input shaft (1) to gear (2) on the reverse shaft. When the REVERSE clutch pack (4) engages, power flows from gear (2) through the clutch to gear (5). Gear (5) transfers power to gear (7) on countershaft (11). When the clutch pack for speed clutch 1 (8) engages, power flows from gear (7) through the clutch pack to gear (10). Gear (10) transfers power through gear (12) to rear output shaft (13).

When the all wheel drive solenoid is energized, the all wheel drive solenoid (22) directs oil to the clutch pack for the front output shaft (15). Gear (18) transfers power from the rear output shaft (13) to gear (17) on the front output shaft (16). When the clutch for the front output shaft (15) engages, power flows from gear (17) through the clutch to the front output shaft (16) .

Power Flow (Second Speed Reverse)

Illustration 24	g00808125
Power flow in second speed reverse (1) Input shaft (2) Gear (3) Reverse clutch piston (4) Reverse clutch pack (5) Gear (6) Gear (7) Gear (8) Countershaft (9) Gear (10) Rear output shaft (11) Clutch pack for speed clutch 2 (12) Clutch piston for speed clutch 2 (13) Clutch piston for the front output shaft (14) Clutch pack for the front output shaft (15) Front output shaft (16) Gear (17) Gear (18) Gear

Illustration 25	g00807921
(19) Solenoid for speed clutch 2 (20) Reverse clutch solenoid

Illustration 26	g00807923
(21) All wheel drive solenoid

When the transmission is in SECOND SPEED REVERSE, the solenoid for REVERSE (20) directs oil to the REVERSE clutch (4) and the solenoid for speed clutch 2 (18) directs oil to the clutch pack for clutch 2 (11). Torque from the engine is transferred through the torque converter to the shaft (1) .

Gear (18) on input shaft (1) transfers power to gear (2) on the reverse shaft. When the REVERSE clutch (4) engages, power flows from gear (2) through the clutch to gear (5). Gear (5) transfers power to gear (7) on countershaft (8). When the clutch pack for speed clutch 2 (11) engages, power flows through the clutch pack to gear (17). Gear (17) transfers power to output shaft (10) .

When the all wheel drive solenoid is energized, the all wheel drive solenoid (21) directs oil to the clutch pack for the front output shaft (14). When the clutch pack for the front output shaft (14) engages, power flows from gear (17) through the clutch to gear (16). Gear (16) transfers power to front output shaft (15) .

Power Flow (Third Speed Reverse)

Illustration 27	g00808127
Power flow in third speed reverse (1) Input shaft (2) Gear (3) Reverse clutch piston (4) Reverse clutch pack (5) Gear (6) Gear (7) Gear (8) Countershaft (9) Gear (10) Rear output shaft (11) Piston for the front output shaft (12) Clutch pack for the front output shaft (13) Front output shaft (14) Gear (15) Clutch piston for speed clutch 3 (16) Clutch pack for speed clutch 3 (17) Gear (18) Gear (19) Gear (20) Gear

Illustration 28	g00807924
(21) Solenoid for speed clutch 3 (22) Reverse clutch solenoid

Illustration 29	g00807925
(23) All wheel drive solenoid

Torque from the engine is transferred through the torque converter to the input shaft (1). When the transmission is in THIRD SPEED REVERSE, the solenoid for REVERSE (22) directs oil to the REVERSE clutch (4) and the solenoid for speed clutch 3 (21) directs oil to the clutch pack for clutch 3 (16).

Input shaft (1) transfers power through gear (20) to gear (2). When the REVERSE clutch (4) engages, power flows from gear (2) through the clutch to gear (5). Power flows from gear (5) to gear (7) on countershaft (8). When the clutch pack for speed clutch 3 (16) engages, power flows from gear (18) on countershaft (8) through the clutch pack to gear (19). Gear (19) transfers power to rear output shaft (10) .

When the all wheel drive solenoid is energized, the all wheel drive solenoid (23) directs oil to the clutch pack for the front output shaft (12). Power is transfered from gear (19) to gear (14) on the front output shaft (13). When the clutch pack for the front output shaft (12) engages, power flows from gear (14) through the clutch to the front output shaft (13).