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In the diagram below, gearboxes for turning on the first
transmission gear 2, move the fork 4 to the left until it engages
with the gearshift z' 1. Then the torque will be transmitted from
the primary shaft 1 through the gears of constant engagement z 3
and z' 3 on the gear z' 1 and z 1 that form the first transmission.
The third gear is activated by moving the synchronizer 2 to
the left. In this case, the driven and driving shafts are rigidly
connected, and the transfer number in the box does not change
and equals one. Such a transmission is called direct and is used
to drive the car at high speed.
The four-speed gearbox has four gears for forward
movement and one for moving back. It acts in the same way as
a three-speed gearbox (Fig. 8.1), but it has design features:
constant gearing of the drive and intermediate shafts, gears of
the second and third gears. The forward gears are activated by
moving the gear of the first transmission and the synchronizer
through the slots of the driven shaft, and the back gear is
activated by the movement of the gear unit of the reverse gear.
Before disassembly it is necessary to drain the oil by
removing the drain plug. Hold the box under the suspension,
raise it with the hoist and install it on the device designed to
disassemble and assemble the gearboxes.
7.4 Individual task. Each student, on the basis of a
positive assessment, receives an individual task for laboratory
work at a poll in the class.
7.4.1 Draw out the principle diagram of the gearbox of the
given vehicle.
7.4.2 Draw a sketch of one of the details of the gearbox.
7.4.3 By the size of the gears to determine their design
parameters, transmission ratio.
7.5 Control questions:
1. What is the purpose of the gearbox?
2. On which wheel drive is the highest torque transmitted?

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