All about Manual Gearboxes and Differentials

There are 3 primary symptoms to look out for when diagnosing Manual Gearboxes:

  • Jumping out of Gear
  • Grating into Gear
  • Noisy

Jumping out of gear – When a vehicle hops out of gear, 99% of the time this is because the gear is worn. The original gear tooth pattern meshes together with a flawless point of contact. Sadly after some time this contact pattern wears out to the red line on the gear tooth and the 2 gears no longer mesh properly. The most well-known cause of this symptom is high mileage and basic wear and tear.

This is the most basic symptom to diagnose because when you drive the vehicle, the gearbox will jump out of gear. We will talk about the diverse options for repair.

Grating into gear – This happens when the synchronizers or synchro rings are worn and they don’t lock onto the gear. Let us have a look at a synchro and where precisely the wear occurs.  

When trying to diagnose this fault, know that the clutch can likewise cause a grating into gear. We ascertain the difference by which gears grate while engaging. On the off chance that the grating occurs when engaging in first gear or reverse while the vehicle is stationary, the grating in usually caused by the clutch. In the event that the grating occurs in some other gears while the vehicle is moving, this is normally brought about by the synchromesh inside the gearbox.

Noise – Noise is by a long shot the most difficult problem to diagnose. The primary causes of noise can be: worn/noisy bearings; gear meshing (wear and tear); lack of oil (Burnt Gears) or Excessive play on the gears/shafts.

  • Bearing Noise – Over time bearings tend to wear down which create an excess of play inside the gearbox allowing the gears and shafts to move around more than they ought to. This results in a whining noise.
  • Gear Meshing – once more, overtime the contact pattern on the gears gradually wears out causing the gears to malfunction resulting in noise. This can likewise be the after effect of a baring wearing away giving the gear more play than it ought to have which thus changes the contact pattern.

Lack of oil – If a manual gearbox keeps running without oil, the internals of the gearbox overheat and burn. Not noticeable to the naked eye, the gear itself and the teeth on the gear lose their shape which will create a noise from that particular gear. Despite the fact that the difference is not obvious, we can tell this effortlessly as the gear will turn blue in colour. 

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