Mechanical three-shaft gearboxes of three types are installed on UAZ vehicles:
- - four-speed, with synchronizers only in III and IV gears;
- - four-speed, with synchronizers in all forward gears;
- - five-speed, with synchronizers in all forward gears.
Four-speed gearboxes are interchangeable, but they can have different sizes of input shaft splines (for different clutch drive discs).
Five- and four-speed gearboxes are interchangeable complete with their transfer cases and cardan shafts.
When installing a five-speed gearbox instead of a four-speed, it is also necessary to refine the hole in the floor of the body for the transfer case levers.
Knots and parts of different gearboxes are not interchangeable.
fig. 1. Gearbox, partially synchronized
fig. 2. Gearbox synchronized
Four-speed semi-synchronized gearbox consists of a one-piece cast iron crankcase in which the primary, secondary and intermediate shafts are mounted on ball bearings.
The front end of the secondary shaft rests on a full complement roller bearing in the bore of the rear end of the input shaft, and the rear end rests on a double-row ball bearing, along which the gearbox and transfer case are centered.
The gears of the intermediate shaft drive, as well as II and III gears are helical, constant mesh.
Splines are installed on the intermediate shaft of the gears of the 2nd and 3rd gears. Bronze bushings with holes and cellular knurling are pressed into the holes of the gears of the II and III gears of the secondary shaft to improve lubrication.
To supply oil to the bushings, radial holes in the gears and helical grooves on the shaft are used.
III and IV gears are switched on by moving the clutches of the inertial synchronizer on the secondary shaft.
The driven spur gear of the 1st gear moves along the splines of the secondary shaft. I gear is engaged by moving the driven gear along the splines of the secondary shaft back, until its teeth mesh with the teeth of the drive gear.
Moving the 1st gear driven gear forward engages the 2nd gear (its splined ring is connected through the 1st gear gear to the output shaft).
In addition, the driven gear has a middle position. In this case, it is used to engage reverse gear.
The reverse gear block is located on a cage needle bearing sliding along an axis pressed into the crankcase.
When the gear unit moves along the axis forward, its large gear engages with the drive gear of the 1st gear, and the small gear engages with the driven gear on the secondary shaft.
At the same time, the primary and secondary shafts begin to rotate in different directions and the car moves back.
The gearshift mechanism consists of a cover in which three rods with forks are installed, a shift lever with a spring, and a spring-loaded fuse that prevents accidental reverse gear engagement.
Fixation of the included gears is carried out by spring-loaded balls included in the holes on the rods.
The locking device in the form of two plungers and a pin on the stem of III and IV gears does not allow switching on two gears at the same time.
The gearbox is lubricated with gear oil poured into the crankcase.
For filling and draining oil, filler and drain holes are used, closed with plugs with conical threads.
Four-speed, fully synchronized transmission differs from the one described in that:
- the inclusion of all forward gears is carried out by moving the clutches of two inertial synchronizers mounted on the secondary shaft;
- - gears of I, II and III gears - helical, constant mesh, mounted on the secondary shaft on double-row roller bearings with plastic separators;
- - the front end of the intermediate shaft rests on a radial roller bearing;
- - the driven gear of the intermediate shaft drive and the leading gear of the III gear are made in the form of a block pressed onto the smooth part of the intermediate shaft;
- - leading helical gears of I, II gears and a spur reverse gear are made integral with the intermediate shaft;
- - reverse gear is engaged by moving the reverse idle gear until it meshes with the spur gearher intermediate shaft and the ring gear of the synchronizer coupling of I and II gears.
In addition, this gearbox has different gear ratios in all gears except IV gear.
Five-speedth gear is designed on the basis of a fully synchronized four-speed and differs in that the fifth gear housing is bolted to the rear wall of its crankcase.
Crankcases are centered with two locating sleeves.
The secondary and intermediate shafts are longer.
A double-row angular contact ball bearing of the output shaft is located in the rear wall of the V gear housing, and an additional radial roller bearing is installed in the bore of the rear wall of the gearbox.
At the rear end of the intermediate shaft, on a double-row needle bearing, a drive (large) helical gear of the 5th gear with an inertial synchronizer is installed.
The driven (small) gear of the 5th gear is located on the splines of the secondary shaft.
When the V gear is on, the secondary shaft rotates faster than the primary, so the V gear is called accelerating.
Thanks to its use, the number of revolutions of the crankshaft is reduced at a high vehicle speed, which increases the engine life and saves fuel.
Lubrication of the 5th gear parts is carried out from the common oil bath of the gearbox.
To reduce oil leakage, a rubber cuff is installed in the cover of the input shaft of the five-speed box.
During operation, check the oil level and change it at the time specified in the lubrication table.
If a leak is found, find out the cause and replace the defective parts (gaskets, plugs, etc.).
Periodically check the fastening of the gearbox, as well as the fastening and adjustment of the gearbox control mechanism on cars of the UAZ-3741 family.
The tightening torque of the bolts and nuts securing the gearbox to the clutch housing and transfer case should be from 39 to 55 Nm (4.0–5.6 kgf m). Gearboxes themselves do not have adjustments.