Transmission System
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Four Wheel drive vehicles (4WD).
These will always have an extra device to split the drive to the wheels so that each axle may
be driven. This device is called a transfer box and will, if the vehicle is full time 4WD, have
and additional centre differential to allow the axles to travel at the differing speeds
necessary on cornering. The extra driven axle will also have a differential. On the diagram
below draw a 4wd layout indicating any differentials, transfer boxes and the position of the
engine and gearbox.
The gearbox and transmission oil levels should be checked periodically.
Safety.
Do not put your finger into the filler plug opening to check the fluid level whenever the
transmission is rotating.
If the vehicle has been driven prior to checking the fluid level, the fluid could be very hot.
Points to note
The vehicle must be level when taking a reading, or the result will be inaccurate.
Using the correct type and grade of lubricant is critical. The wrong selection can lead to
premature failure of the internal components.
Refer to the manufacturer’s recommendations for the specified intervals and exactly where
to check the oil level.
1. After identifying the filler plug clean the area around the filler plug to keep dirt out
of the system As a precaution, place a drain pan under the plug to catch any fluid that
may leak out.
2. Remove the filler plug with the correct tool to prevent damage to the plug, and check
the level at the bottom of the filler plug opening. If fluid begins to leak slowly, then
the system is full. Immediately replace the plug. If the level is down, you will need to
add fluid of the correct type and grade to bring it up to the recommended level.
Check the plug for damage to the thread, and sealing gasket if it exists. Install a new
gasket. Replace the filler plug and tighten it with the correct tool to the
manufacturer’s recommended tension.
3. Check final drive oil level
Repeat for the final drive if separate or for any other transmission housings on 4
wheel drive vehicles.
Clutch mechanism
The clutch provides a smooth take up of
drive and a temporary neutral. The clutch
adjustment must be checked as it reduces
as the clutch wears. There should be either
15mm of free-play at the pedal (type 1) or
the pedal should be adjusted to the same
height as the brake pedal (type 2).
Fluid types are self adjusting but check the level
of fluid in the master reservoir.
Drive shafts.
These are fitted on FWD vehicles and have Constant Velocity(CV) joints to allow the shaft to
rotate the wheel even when it is turned.
Check the rubber ‘boot’ or cover for integrity and ensure there is no rotational movement in
the joint itself. Check the clips retaining the cover.
Wheel bearings
Each wheel normally has 1 pair of bearings that allow the wheel to rotate, yet keep it from
having any lateral radial or axial movement.
These must be checked for free rotation, lack of coarseness and noise, and correct
adjustment.
Check the settings from the data book and perform the task accordingly. This may have a
torque setting (i.e. 15n/m) or an additional angle setting (i.e. 35n/m +60°)
Double row angular ball bearing image - http://img.directindustry.com/images_di/photog/double-row-angular-contact-ball-bearing-413230.jpg