Gearbox control mechanism


The gearbox control mechanism consists of a gearshift mechanism and a range-selector mechanism with an electrohydraulic system for shifting into high (H) and low (L) stages of the gearbox reduction gear.
The Gearshift Mechanism is mounted in the transmission gear assembly, the fork box (7) (see Figure “Gearbox (24F+12R)”) and in the control mechanism cover (14).


The dogs with the first, second and fifth, sixth gear-shift forks fitted thereon are installed in the cover (54). The dogs are fixed in the cover by means of ball-point locks. The position of the forks is adjusted by means of tapered adjusting screws.


Gear shift mechanism
1 – fork; 2 – boot; 3 – sphere; 4 – spring; 5, 7 – pins; 6 – housing; 8 – cover; 9 – shaft; 11 – bolt; 12 – bushing; 13 – cover; 14 – sunk key; 14, 20 – lever; 16 – sensor; 17 – screw; 18 – washer; 19 – check ring.

In the fork box (7) (see Figure “Gearbox (24F+12R)”), the three dogs, fork (8), ball-point lock (13) and parts of the inter-lock mechanism for preventing the simultaneous engagement of two gears are installed. The fork box is fastened to the gearbox housing (1).

A shaft (9) with attached lever (15) and bushing (12) is installed in the cover (13) supports and the housing (6) (see Figure “Gearshift Mechanism”); the two bushings (18) and spring (10) are mounted between the check rings (19). The bushings rest against the screw (17) and the housing (6) end-face with their ends. This mechanism serves for positioning the gearshift lever to its neutral position. The shaft (9) is connected with the fork (1), to which the gearshift lever is attached, by means of the dogs (5) and (7), and lever (20). The fork (1) is installed in the housing (6) through a sphere (3); it is supported by spring (4).
The Range-Selector Mechanism is mounted in the gearbox housing (1) (see Figure “Gearbox (24F+12R)”) and in the gearshift mechanism cover (14).
The fork (37) for shifting the toothed coupling (36), fork for shifting the toothed coupling (6) (see Figure “Shaft of reduced gears and reverse”) and fork (18) for shifting the synchronizer (26) (see Figure “Gearbox (24F+12R)”) are mounted on the dogs in the housing (1). The dogs are fixed in the housing with ball-point locks.

The shaft (9) with the levers (10) keyed thereon is installed in the supports of the cover (12) and housing (18) of the control mechanism (see Figure below). The shaft (9) is fixed with a ball-point lock (14) and connected with the fork (1), on which the range-shift lever is fitted, through the dogs (5) and (7) and lever (6). The fork (1) is installed in the housing (18) in sphere (3) and supported by spring (4).


Range shift mechanism
1 – fork, 2 – boot, 3 – sphere, 4 – spring, 5, 7 – pins, 6, 10 – levers, 8, 12 – covers, 9 – shaft, 11 – gate, 13, 17 – keys, 14 – ball-point lock, 15 – nut, 16 – bolt, 18 – housing.

The Higher-Lower Stage Selection Mechanism of the Reduction Gear of the gearbox (see Figure below) is mounted on the shifting mechanism cover and consists of a cylinder (11) secured on axle (12), pusher (7), and lever (5) fixed on the spindle (4). The pusher (7) is jointed with the lever (5) by means of pin (6). The lever on spindle (4) comes into engagement with the dog of fork (18) (see Figure “Gearbox (24F+12R)”) and, when the spindle turns, shifts the synchronizing sleeve (26). The position of the lever (5) (see Figure below) is adjusted by changing the pusher (7) length, with further locking it with lock-nut (8). The cylinder (11) is connected to the hydraulic system through an electrohydraulic valve (14). The sensor (15) connects the valve (14) to the electrical circuit only when the gearshift lever is in its neutral position. The drawn-in position of the cylinder (11) rod corresponds to the lower "L" stage of the gearbox reduction gear.

Sensors (10) serve to indicate that the reduction gear stage is engaged. For adjusting the cylinder (11), move the piston into the cylinder as far as it will go. Turn the lever (5) counter-clockwise having engaged the reducing range of the gearbox reduction gear. Screw in the pin (7) by 8-9 revolutions and lock the same by means of the nut (8). Align the holes in the lever (5) and fork (16) nu screwing the fork (16) in or out and lock the same with a nut. Turn the lever (5) clockwise having engaged the speeding-up range of the gearbox reduction gear. Draw out the rod of the cylinder (11) and align the holes in the lever (5) and those in the fork (16). Connect the lever (5) and the fork (16) by means of the pin; then refit the washer and the cotter pin. Turn the (18) in or out until the spherical part of the bolt rests against the lever (5) and lock the same with a nut.


1 – gearshift fork, 2 – range-shift fork, 3 – bolt, 4 – spindle, 5 – lever, 6 – pin, 7 – pusher, 8 – lock-nut, 9, 13 – oil pipelines, 10 – pressure sensor, 11 – hydraulic cylinder, 12 – axle, 14 – electrohydraulic valve, 15 – sensor; 16 – fork; 17 – bracket; 18 – adjusting screw.