The transmission is manual with manual shift, has five forward gears and one reverse, all forward gears are synchronized.
The body parts of the box - the clutch housing, the gearbox housing itself and the rear cover - are cast from aluminum alloy and are tied together with studs with nuts.
The joints are sealed with cardboard gaskets (a sealant can be used during repair).
To improve the heat sink, the surface of the gearbox crankcase has ribs.
From below, the crankcase is closed with a stamped steel lid with a gasket (fastening - on studs).
The clutch housing is bolted to the engine cylinder block.
To ensure the alignment of the crankshaft of the engine and the primary shaft of the gearbox, the crankcase is centered on two bushings (grooves are made under them in the mounting holes of the block and the crankcase).
The third support of the power unit is installed on the rear cover of the gearbox.
It is attached to the crossbar, and the latter to the floor of the body (on welded bolts).
- first gear 3.67
- second gear 2.10
- third gear 1.36
- fourth gear 1.00
- fifth gear 0.82
- reverse gear 3.53
There is a filling (control) hole in the gearbox crankcase on the left side, and a drain hole in the lower cover of the crankcase.
The holes are closed with plugs with a conical thread.
There is a magnet in the drain plug. It detains steel particles that get into the oil when the parts wear out.
A breather is screwed into the upper part of the clutch housing.
It prevents the pressure in the gearbox from increasing when it is heated.
In case of malfunction of the breather (jamming of the cap), a strong oil leak through the seals is possible.
There are three shafts in the gearbox: primary, secondary and intermediate.
The primary shaft is supported by two ball bearings located at the rear end of the crankshaft and in the front wall of the gearbox crankcase (the latter perceives the bulk of the load).
A needle bearing is installed in the rear end of the primary shaft, which is the front support of the secondary shaft and ensures the alignment of the shafts.
The secondary shaft also relies on a ball bearing in the rear wall of the gearbox crankcase and a roller bearing in its rear cover.
The intermediate shaft rotates in two bearings:
the front - two-row ball is located in the front wall of the gearbox crankcase, the rear - roller is located in its rear wall.
The primary shaft has two gear rings. The bevel-toothed crown, located closer to the front wall of the crankcase, is in constant engagement with the front gear of the intermediate shaft (thus these shafts always rotate together).
The straight-toothed crown of the primary shaft is the crown of the synchronizer IV transmission (when it is turned on, the torque is transmitted directly from the primary shaft to the secondary, bypassing the intermediate, so this transmission is often called "direct").
The intermediate shaft is a block of four bevel gears.
When any gear except IV is engaged, the torque is transmitted to the secondary shaft through the intermediate one.
The gears of the intermediate shaft are arranged in the following order (from its front end): the gear of permanent engagement with the primary shaft, gears III, II and I gears.
A block of two gears is bolted to the rear end of the shaft: reverse gear (straight-toothed) and V gear (oblique-toothed). It additionally relies on a roller bearing in the rear cover of the gearbox.
On the secondary shaft there are driven gears III, II, I gears, reverse gears and V gears (in order, counting from the front end of the shaft) and synchronizers.
The driven gears of the forward gears are in constant engagement with the corresponding gears of the intermediate shaft.
The gears V, III and II of the gears rotate on the hardened necks of the secondary shaft, the gear I of the transmission is on the bushing.
Involute slots are used to fix the reverse gear and the hubs of the synchronizer V gear clutch on the secondary shaft.
A locking ring is installed on the secondary shaft, located between the synchronizer hub and the driven gear of the V gear.
At the same time with the bevel gears of the forward gears, the toothed crowns of their synchronizers are made — straight-toothed gears of smaller diameter.
They are directed towards the corresponding synchronizer (III, I, V - forward, II - backward).
At the rear end of the secondary shaft, the flange of the elastic coupling is fixed with a nut.
The synchronizer consists of a hub rigidly fixed to the secondary shaft, a sliding clutch, a locking ring, a locking ring and a spring with a washer.
The hubs of the synchronizers III- IV and I- II gears enter the grooves on the secondary shaft with internal protrusions, and the synchronizer hub at the transmission is held by the same key as the driven reverse gear.
There are slots on the outer surface of the hubs, along which sliding couplings move. There are recesses on the couplings, which include forks of the gearshift rods.
The locking rings are connected by their inner crowns to the crowns of the synchronizers of the corresponding gears and are compressed by springs towards the sliding couplings.
The springs rest on the side surface of the driven gears through washers.
The reverse gear does not have a synchronizer.
To turn it on, you need to engage the intermediate reverse gear with the driven gear of the secondary shaft and the drive gear of the transmission unit.
The axis of the intermediate reverse gear is attached to the rear wall of the crankcase of the box.
The gearshift mechanism consists of a guide plate with eight rectangular cutouts in the center, upper and lower washers, a gearshift lever and its housing.
These parts are tightened with three bolts. The gear selection mechanism is attached with three studs to the back cover of the box.
The neutral position of the lever between the III and IV gears is set by two pairs of spring-loaded guide bars installed in the grooves of the guide plate and acting on the lower end of the lever.
The gearshift drive consists of three rods connected to the forks. The forks of the forward gear are included in the grooves of the sliding couplings of the synchronizers, and the fork of the reverse gear is included in the groove on the intermediate gear.
Accidental activation of reverse gear instead of V gear is impossible due to the locking stop attached to the fork of the thrust tip and the locking pad fixed on the upper body of the gear lever.
To turn on the reverse gear, you need to press the lever down — at the same time, the locking stop falls below the locking pad.
Transmission parts are lubricated by spraying.
The primary and secondary shafts are sealed with oil seals.