Knowing the signs of a faulty gearbox means you can get repairs done before the damage becomes serious - potentially saving you money.

It's important to address gearbox issues early - or you'll simply be storing up more serious gearbox problems for later on.

 

Why is gearbox failure so significant?

Your gearbox - or transmission - is critical to the effective, safe functioning of your vehicle.

Unlike a broken tail light, for example, a faulty gearbox could mean your car is put out of action, and may result in you being stranded by the roadside.

But how do you tell if a gearbox is damaged?

Oil leak from engine on road

Gearbox problems: What are the signs of gearbox failure?

There are key gearbox failure symptoms to keep an eye out for - Here’s 10 signs of how to tell if a gearbox is damaged.

 

Fluid leakage

Automatic transmission fluid (ATF) is present in automatic gearboxes to help reduce friction and therefore overheating. If this fluid begins to leak, you could have a serious problem on your hands.

Indeed, loss of ATF is a very common cause for automatic transmission failure.

An ATF leak may result in bright red fluid pooling under your vehicle. However, if the fluid has been burnt in the gearbox due to friction, it could be brown or black - in which case a major repair to your gearbox is likely required.

 

Check Engine Light

While the Check Engine Light can suggest a variety of issues, it may also mean you have a gearbox fault.

Don't be tempted to ignore this warning; your car has many sensors designed to accurately detect problems - hopefully before they become serious.

Check your coolant and transmission levels, or take your vehicle to a mechanic to be checked over for any gearbox problems, or other potential issues.

 

Poor response from your car gearbox

If you're having trouble shifting gears, your vehicle may have a faulty gearbox.

Any sign of hesitation - or complete refusal - to change gears may indicate your gearbox may have a fault. These symptoms may be be a sign of electric, hydraulic or mechanical issues with your gearbox.

If you have gearbox damage, in a manual, you may notice a disconnect between changing gears and the actual increase in revs from the engine. The vehicle may also accelerate more slowly than the higher revs suggest.

 

Unusual sounds

Unusual sounds could also be an indication that you have a damaged gearbox.

You may have a problem with your gearbox if it starts making a sound you’ve never heard before, or if you hear clunking, whining, humming or buzzing.

Your gearbox comprises hundreds of moving parts. If just one ball bearing is faulty, for example, such unexpected noises may result.

Gearbox bearing failure symptoms on manual transmissions tend to "clunk" while automatics often hum or buzz.

Beware that such noises may also be caused by problems with the exhaust, drive shaft or engine, and may not mean that your gearbox is faulty - but either way, it's important to get the vehicle checked out by a trusted mechanic.

 

Shaking, jerking or grinding

With a vehicle with a gearbox bearing failure symptoms, you may experience shaking, jerking or grinding while behind the wheel.

Automatic gearbox issues often involve hesitation, slipping, or trembling during gear changes. Manuals are more likely to "grind" when suffering a gearbox fault.

Engine and transmission mounts are often the source of jerking and clunking.

 

Burning smell

If you notice a rubber-like burnt smell accompanied with fluid leakage, you could have a transmission issue. You may also see smoke.

Burnt fluid means that your transmission is not getting the lubrication it needs.

These signs may suggest your transmission is nearing the end of its life.

If there's no leakage, such a smell may be caused by sludge or debris being burnt.

Gearbox and clutch cross section

Refusal to shift gear

There are multiple possible reasons why your car won’t change gear, including incorrect transmission fluid, a clogged filter, faulty sensors and failing solenoids.

It’s important to get your vehicle checked out by a professional if it refuses to change gear.

 

Quaking when in neutral

If your gearbox quakes or bumps when in neutral, you may need to replace the transmission fluid. But it may also suggest something more serious.

Either way, it’s best to get it checked out by a trained mechanic.

 

Gear slippage

A bad gearbox symptom, slipping gears is never a good sign, and may place you, your passengers, other drivers or even pedestrians in danger. Sudden braking or acceleration may be required to avoid collisions.

Many modern vehicles feature a “limp mode” or a “safe mode" which prevents drivers from proceeding with a damaged gearbox by defaulting to a single gear.

Gear slippage means you should visit a mechanic immediately.

 

Dragging clutch (manuals)

A dragging clutch happens when the clutch disc and flywheel fail to disengage when the clutch pedal is depressed.

Manuals may also pop out of the current gear - and a grinding noise may be heard.

 

Replacing your gearbox

When you are looking to buy a gearbox to replace your old one it is important to match up the part numbers to be sure it’s the correct one for your car. 

 

Different transmission types

Today there are over 200 transmission types on the road. Some car manufacturers will even change the types or designs of transmissions on different car models from year to year, whilst some car models may well have three or four types based on the engine size.

 

How do I know what gearbox is in my car?

The gearbox code is usually a code with a mixture of numbers and letters. Some car manufacturers will put the code into the owners manual.

Alternatively, the gearbox code can be found on the gearbox. The location of the gearbox code is dependant on the manufacturer of the car , but it will be either stamped into the gearbox or on a sticker on the gearbox.