The gearbox is a very important component of the transmission system in an automobile. The gearbox receives power and torque from the engine, in reality, the gearbox is always attached to the engine irrespective of the car manufacturer.
In manual transmission, the gearbox is always attached to the clutch plate and clutch disc which is then attached to the engine. The function of the clutch plate in the manual transmission is to transfer the clutch grip from the clutch to the flywheel which transfers it to the rotating wheels.
In automatic transmission, there is no clutch plate but instead a torque converter and this does effectively what is necessary by it. The gearbox is definitely important in transmission system, the gearbox is connected to the engine and axle. Some cars use two axles, one connected to the front wheels and the other one being connected to the rear wheels.
Even sometimes, the transmission system may be faulty but mostly it may not be as a result of a faulty gearbox. The rear axle causes some noise whenever faulty. How do you diagnose rear axle noise??
a. Noise occurring when the vehicle is pulling and the cause of this would possibly be insufficient clearance between the gear teeth.
b. Noise occurring on over-run and the only cause would be either too much clearance in the end play in the pinion assembly.
c. Noise occurring when the vehicle is entering a corner and this would be a faulty differential gear, it is either damaged teeth or excessive wear.
In general, a noisy axle may be short of oil or the viscosity may be incorrect or alternatively, there may be excessive wear on the gear teeth or bearings.