Tractor Gearbox 12+24


The tractor gearbox (24 forward + 12 reverse) consists of a transmission assembly, a shaft of reduced gears and reverse, a secondary shaft supported in bearings in the housing as well as a control mechanism and electrohydraulic system units.

The Transmission Assembly is mounted on the cover (54) and consists of the primary shaft (51) with driving pin-ions (2, 4, 6, 10), supported in needle bearings, riding thereon. These gears provide for shifting in the fifth, sixth, third and fourth gears, respectively. The first speed driving pinion is made integral with shaft (51) and the second speed driving pinion is rigidly connected to the shaft. The needle bearings are lubricated under pressure through oil pipe-line (53) and drillings in the shaft. Two inertia-type synchronizers (4) and (9) are sliding on the shaft splines; they provide for shifting between fifth and sixth, third and fourth speeds. The primary shaft is supported in the roller bearings housed in cover (54) and in housing.



Longitudinal section of the gearbox:



1 – housing; 2, 4, 5, 6, 10, 17, 19, 20, 31, 32, 34, 39, 40, 41, 43, 44, 45 – gears; 3, 9, 26, 42 – synchronizers; 7 – fork box; 8, 18, 37 – forks; 11, 23, 25, 27, 28, 30, 35, 38, 46, 49 – bearings; 11, 15, 47, 50 – nuts; 13 – ball-point lock; 14 – control mechanism; 16, 21 – adjusting shims; 22 – bearing seat; 24 – secondary shaft; 29 – independent PTO drive shaft; 33 – gear cluster shaft; 36 – toothed coupling; 48 – intermediate shaft; 51 – primary shaft; 52 – lubricant feed sleeve; 53 – oil pipeline; 54 – cover.



The driven gears (45, 44, 40 and 39) of fifth, sixth, third and fourth speeds, respectively, are interference fitted onto the intermediate shaft (48). Driven gears (43) and (41) for shifting into first and second speeds, respectively, are sup-ported in needle bearings. An inertia-type synchronizer (42), which helps to engage the first and second speeds, is splined to the shaft.


The Reduced Gears and Reverse Shaft 3 (see Figure below) is supported in bearings (1) and (12), installed in the housing (4). The shaft carries a driven gear (10), which is secured to the shaft by means of the bushings (9), driving forward run pinion (8) and reverse run gear (5), both supported in needle bearings. These gears are connected to the shaft through a toothed coupling (6). The bushing (16) splined on the shaft is stopped with a check ring (7). Should the tractor is equipped with a creeper, a gear to be engaged with the creeper one is mounted instead of the bushing (9).


Shaft of reduced gears and reverse
1,12 – bearings; 2, 13 – nuts; 3 – shaft; 4 – housing; 5, 8, 10 – gears; 6 – toothed coupling; 7 – check ring; 9 – bushing; 11 – cover; 14 – oil feed sleeve; 15 – oil pipeline; 16 - bushing.

The Gear Cluster Shaft (33) (see Figure “Gearbox (24F+12R)”) is installed in the housing (1), supported in bearings (27) and (35). The gears (32) and (34) are splined to the shaft and stopped with a check ring. The driven gear of the synchronous PTO (31) sits on the shaft in roller bearings (28) and (30).

The Secondary Shaft (24) (see Figure “Gearbox (24F+12R)”) is installed in the housing (1), supported in conical roller bearings (23) and (25), the latter are adjusted by adjusting shims (16), while the position of the shaft bevel gear relative to the housing end-face (dimension 15-0.15) is adjusted by the selection of adjusting shims (21). A driving pinion (20) of the synchronous PTO and the front drive axle as well as the synchronizer hub (26) is immovably fitted on the shaft. The driven gears (17) and (19) are installed though needle bearings; they are pressure-lubricated through drillings in the shaft. The gear shifting is achieved by means of a synchronizer (26) and fork (18) fixed on a dog. The dog is installed in the recesses of the housing (1) and locked with a ball-point lock.

The sets of parts installed on the primary, intermediate and secondary shafts and the shaft of reduced gears and reverse are tightened up with nuts (12, 15, 47 and 50).