What are the signs of a cars gearbox failing?

In short, gearbox problems usually show up as slipping or hard shifting, strange noises, warning lights, and issues with transmission fluid or leaks. If you notice these symptoms, have the transmission inspected promptly to avoid further damage.

Automatic transmissions: common signs

Automatic gearboxes (including CVTs) rely on hydraulic pressure and electronics; the following symptoms are commonly observed when an automatic transmission starts to fail.

Common causes behind these symptoms

Problems can include worn clutches or bands, faulty solenoids, valve-body wear, low or degraded transmission fluid, overheating, or internal gear damage. A professional diagnosis is needed to confirm the exact cause.

• Slipping gears: the transmission shifts out of the current gear unexpectedly or engine RPM rises without proportional acceleration.


• Delayed or failed engagement: there is a noticeable pause when selecting Drive or Reverse before the car moves.


• Harsh or abrupt shifts: gear changes occur with a jolt, clunk, or jerk.


• Unusual noises: whining, grinding, banging, or clunking noises while driving or shifting.


• Warning lights or fault codes: the transmission warning light or the check engine light may illuminate.


• Fluid issues: transmission fluid leaks, low fluid level, or fluid that is dark, dirty, or burnt-smelling.


• Overheating or limp mode: the car may overheat or enter a reduced-power limp mode to protect the transmission.


• Poor movement or lack of responsiveness: the car struggles to move or remains stuck in a gear.

These signs can overlap with engine or driveline problems, so a proper diagnosis is essential to determine if the gearbox is failing or another component is at fault.

Manual transmissions: signs to watch

Manual gearboxes rely on the clutch and synchronizers; signs tend to center on clutch performance and gear engagement.

Common causes behind these symptoms

Worn or overheated clutches, hydraulic clutch problems, worn synchronizers, or damaged linkages can cause difficulty or damage when shifting.

• Difficulty shifting or grinding when selecting gears: you may hear grinding or feel resistance when moving the gear lever into gears.


• Heavy, sticky, or spongy clutch pedal: the pedal may feel hard to press or fail to return smoothly.


• Clutch slipping: engine revs rise without a corresponding increase in vehicle speed, especially under load.


• Burning smell from the clutch: indicates excessive clutch heat and wear.


• Clutch leakage or pedal feel changes: hydraulic system leaks around the pedal or under the car.


• Difficulty engaging first gear or reverse: gear engagement is difficult, occasionally grinding or pops out of gear.


• Unusual noises when engaging or releasing the clutch: clunks, chirps, or grinding sounds.

As with automatic transmissions, these signs can point to clutch or gearbox problems, so a trained technician should diagnose and advise on repairs or replacement.

What to do if you notice signs

If you notice any of the symptoms above, take these steps to protect your car and avoid costly damage.

• Check transmission fluid level and condition (automatic transmissions use red or pink fluid; dark or burnt smell indicates degradation).


• Look for leaks under the vehicle and around the transmission area; address fluid loss promptly.


• Note any warning lights and record the symptoms to share with a mechanic.


• Avoid long drives or towing if slipping, flaring RPMs, or loss of drive occurs; have the vehicle towed if necessary.


• Consult a qualified mechanic or transmission specialist for diagnosis, repair, or possible replacement.

Professional diagnosis may involve road testing, fluid pressure checks, pan inspection, and sometimes internal diagnostics. Early detection helps prevent further damage and reduces repair costs.

Summary

Gearbox problems manifest as gear slippage or hard shifting, noises, warning lights, and transmission-fluid issues for automatics, and clutch-related symptoms for manuals. If you observe any of these signs, schedule a professional inspection promptly to determine the right course of action and protect your vehicle’s driveline.

What does a failing gearbox sound like?

A bad gearbox can sound like whining, humming, grinding, clunking, or buzzing. These sounds may be more noticeable when shifting gears or when the vehicle is in motion, and they can indicate problems like low fluid, worn bearings, or damaged gears. 
This video discusses the sounds a failing transmission might make, such as whining, grinding, and clunking: 48s8020 AutomotiveYouTube · Nov 19, 2023
Specific gearbox sounds and their potential causes

• Grinding: This often happens when shifting gears and can be caused by a worn-out clutch or damaged synchronizers. It can also indicate a damaged planetary gear. 
• Whining or humming: A persistent whining or humming sound can indicate a problem with the transmission fluid pump or low transmission fluid levels. 
• Clunking or banging: These noises may point to loose gears or a loose clutch. It can also be a sign of issues with the transmission mounts. 
• Buzzing or vibrating: This could signal a problem with the torque converter in an automatic transmission. 
• Clicking: A constant clicking or whistling noise could be a sign of worn-out bearings. 

This video demonstrates the sound of a failing transmission when shifting gears: 57sDrews Quick Fixes Hacks And ReviewsYouTube · Jan 6, 2021
Other signs of a failing gearbox

• Delayed or harsh shifting: The transmission may feel slow to engage a gear, or the shift may be rough. 
• Slipping: You might experience a loss of power and acceleration as the engine revs high, but the vehicle doesn't gain speed. 
• Fluid leaks: Leaking transmission fluid is a clear sign of a problem. 
• Burning smell: A burning smell, along with noise, is a serious warning sign. 

You can watch this video to learn about other symptoms of a bad transmission: 47sEasyAutoFixYouTube · Mar 31, 2021

How much does it cost to fix a gear box?

Gearbox repair costs vary widely, but simple repairs can range from around $200 to $1,000, while a major internal overhaul might cost $1,500 to $3,000 or more. The final price depends on the type of repair needed, your car's make and model, and labor costs, with automatic transmissions typically being more expensive than manual ones due to their complexity.
 
Factors that influence the cost

• Type of repair: Minor fixes like a sensor replacement cost less than a complete transmission rebuild or replacement. 
• Manual vs. Automatic: Automatic transmissions are generally more expensive to repair or replace because they are more complex and have more electronic components. 
• Make and model: Luxury, high-performance, or imported vehicles can have significantly higher costs than standard domestic models. 
• Labor costs: Labor charges vary by location and the complexity of the job. Extensive disassembly or specialized tools increase labor time and cost. 
• Parts: The choice between original equipment manufacturer (OEM) parts and aftermarket or used parts can affect the final price. 

Cost examples for different repairs

• Basic repairs: $200–$1,000 
• Minor internal repair: $300–$1,500 
• Manual transmission clutch replacement: $500–$1,500 
• Major internal repair (rebuild): $1,500–$3,000+ for automatic, $800–$2,000 for manual 
• Transmission replacement: $1,500–$4,000+ for manual, $2,000–$4,000+ for automatic 

How does a car act when the transmission is going out?

A car with a failing transmission will often exhibit symptoms like slipping gears, rough shifting, and strange noises such as grinding, humming, or clunking. Other signs include a burning smell, visible fluid leaks, a check engine light, and a delay or complete inability to engage gears, especially when trying to move in reverse or accelerate from a stop. If a transmission completely fails, the car will likely not move at all, even when the engine is running. 
This video demonstrates what transmission slipping looks and sounds like: 1mEasyAutoFixYouTube · Mar 31, 2021
Common symptoms

• Slipping gears: The engine may rev loudly, but the car's speed does not increase proportionally. This is often described as "feeling like you're going nowhere fast". 
• Rough or delayed shifting: Gear changes feel harsh, with clunks, hesitations, or jerking. The car may struggle to shift into a different gear, especially at odd times. 
• Unusual noises: Listen for grinding, clunking, buzzing, or humming sounds coming from the transmission area, especially during shifts or while in neutral. 
• Leaking fluid: A reddish or brown fluid leak under the vehicle is a common sign of a transmission problem. Low fluid can cause overheating and damage internal components. 
• Burning smell: A burnt-toast or burning oil smell can indicate that the transmission fluid is overheating or that internal components are breaking down. 
• Stalling or no power: The car may not move at all when put into gear or may feel like it has no power when accelerating. 
• Shaking or vibrating: The vehicle may shake or tremble, particularly during gear changes. 

This video explains what a failing transmission sounds like: 14sScotty KilmerYouTube · Sep 6, 2021
What to do if you experience these symptoms

• Immediately turn on your hazard lights and pull over to a safe location. 
• Do not continue to drive the vehicle, as this can cause further damage. 
• Call a towing service to have your car taken to a mechanic for diagnosis and repair. 

How do I know if my gearbox is bad?

Automatic gearbox telltale signs include hesitation, slipping, or “trembling” during gear changes. Manuals are more likely to grind. Jerking and clunking noises are more likely to be caused by failing engine and transmission mounts.