Process and Precautions in Repairing Manual Transmission System

This article discusses the process and precautions necessary when repairing manual transmission system in heavy vehicle. It also describes the process for repairing manual transmission and the testing guidelines.

Process and precautions in repairing manual transmission system
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Discuss the process and precautions necessary when repairing manual transmission system in
heavy vehicle.
The heavy trucks transmission system should be well maintained throughout the vehicle
lifetime. This is important for long term transmission health. Transmission system converts the
force from engine into useful power source. The system has series of gears and acts as a link
between the engine the vehicle wheels. A manual transmission system has clutch which is used
to change gears ("Transmission Inspection, Repair and Replacement Cost | AutoGuru", 2019).
The process involved in repairing a transmission system requires the basic knowledge of
transmission repair. The following are the basic precaution measures which should be observed
in repairing transmission systems
 The repair technician should be aware of jack capability in supporting the manual lifting
weight
 Mechanics should employ correct lifting techniques when handling the transmission
systems
 Removal and replacement of transmission system should be done carefully to avoid any
mechanical hitches that could result
 Always inspect the clutch functionality
 Get to understand the lubrication of the transmission system
Repairing the transmission system involves crucial processes which should be taken care of.
This involves identifying the fault in the transmission system. The identified faults will later
form the basis for repairing the transmission system. In most cases, the gear coupling is the
source of all the faults. Repairing the transmission system therefore should consider careful
inspection of the gear system. If the gear system is faulty, careful and thorough check should
follow. Check the gear selector, housing couplings and the mountings
Describe the process for repairing manual transmission
Gears in manual transmission system are controlled by the driver.
Repairing transmission system involves series of activities which have been discussed below.
Identifying the fault
Mechanic should be aware of what problem he has to solve. Identifying the problem
involve thought check. The dynamic check of system will involve inputting the driveline with
testing parameters, the test will be done with wheels connected to drive shaft hanging. The
mechanic then runs the engine, tests the clutch functionality while observing the vehicles
behavior.
Gathering the necessary information will form the basis of repair. The following are to be
addressed

 Check gear behavior i.e. gear jumps
 Check the vehicles unnecessary noise
 are there any leaks
 Is the fault affecting one or all gears?
 Is the fault happening at certain speed or?
 Happens when turning
 Identify if the fault happened after rectifying problems related to clutch or other
parts
The vibration and clunking noise from the heavy vehicle will form basis for the repair
Preforming the transmission repair
After identifying the problem, the transmission system will be removed for repair.
Remove the gear system and the transmission shaft.
Repairing the gear system
Check the functionality of gear selector lever, if not working as expected, replace it. For
good functionality, replace the housing of the system. Use new couplings and mount the system
with mountings in good condition. Check the gear teeth and gear addendum
Figure 1 sample gear system ("Gears - How do they work? - Different types explained and
compared", 2019)
Check if the gear linking work perfectly. The external linkages must mate with the gear system
for effective transmission. Adjust the gear linkages in case of any misalignments. Check if the
gears respond well by adjusting the clutch and the gear lever.
Shaft system
Check if there is any fault in shaft alignment.

Figure 2 showing powertrain shaft, part of heavy vehicle photo from auto guru website 2019
When the shaft is in good condition, replace the shaft seals.
Check the shaft bearing as shown in picture below

Figure 3 showing exploded view of the shaft system ("REAR AXLE", 2019)
Dismantle the system as shown on picture above, then replace the bearings and the seals for the
system.
Transmission system assembly
Ensure that all the repairs have been done carefully. Assemble the shafts system.
Assemble the gearbox and link it to the shaft. Always follow the manufacturers manual to ensure
that all specifications are met. Insert the system into the vehicle(Soto, 2012). Ensure everything
is set up well.
Others minor issues
Ensure the transmission system is well lubricated, check oil level.
Test the clutch lever if it connects efficiently to the gear.
Correct the leaks if any.
Testing

To ascertain that the faults are repaired, the mechanic will drive the heavy vehicle. The following
guidelines will help in testing
 Test should be made at multiple speeds
 Test for both reverse and forward
 Check noise, gear behavior and any oil leaks

References
Gears - How do they work? - Different types explained and compared. (2019). Retrieved from
https://www.explainthatstuff.com/gears.html
REAR AXLE. (2019). Retrieved from https://www.mazdabg.com/ftp-uploads/Mazda/--Repair
Instructions--/Mazda MPV Pickup Navajo 2/8964R07_REAR_AXLE.htm
Soto, X. (2012). Automotive Engineering. New Delhi: World Technologies, pp.12
Transmission Inspection, Repair and Replacement Cost | AutoGuru. (2019). Retrieved from
https://www.autoguru.com.au/car-advice/repair-tasks/transmission-inspection-repair-and-
replacement