What happens if I dont change my differential fluid?

If you don't change your differential fluid as recommended by the manufacturer, it can lead to several problems with your vehicle's differential. The differential is a critical component that transfers power from the transmission to the wheels, and it requires regular maintenance to function properly.

Increased Wear and Tear

Over time, the differential fluid breaks down and becomes contaminated with metal shavings, dirt, and other debris. This can cause increased wear and tear on the gears and bearings inside the differential, leading to premature failure. Failing to change the fluid can result in expensive repairs or even a complete differential replacement.

Reduced Lubrication

The differential fluid is responsible for lubricating the moving parts inside the differential. As the fluid degrades, it loses its ability to effectively lubricate the gears and bearings. This can cause increased friction, heat, and wear, ultimately leading to a breakdown of the differential.

Decreased Fuel Efficiency

When the differential fluid is old and contaminated, it can increase the amount of effort required to turn the wheels. This results in increased resistance and decreased fuel efficiency, costing you more money at the pump.

Potential Differential Failure

If the differential fluid is not changed as recommended, the increased wear and tear, reduced lubrication, and decreased fuel efficiency can eventually lead to a complete differential failure. This can be a costly repair, often requiring the replacement of the entire differential assembly.

Recommended Maintenance

To avoid these issues, it's important to follow the manufacturer's recommended maintenance schedule for changing the differential fluid. This is typically every 30,000 to 60,000 miles, depending on the vehicle and driving conditions. Regularly changing the differential fluid can help extend the life of your vehicle's differential and prevent costly repairs down the line.

How to tell if your rear differential fluid needs changing?

You can tell your rear differential fluid needs changing by listening for unusual noises like whining, humming, or grinding, and by observing performance issues such as difficulty turning, vibrations, or uneven tire wear. Visible signs like leaks on the ground, a burning smell, or fluid that appears dirty, thick, or contaminated also indicate a problem.
 
This video explains how to check and change the rear differential fluid: 56s2CarProsYouTube · Sep 21, 2013
Auditory and performance signs

• Noises: Listen for whining, howling, or humming noises that may change with speed or when turning. Clunking or grinding sounds can also be a sign of poor lubrication. 
• Vibrations: Notice if you feel unusual vibrations or shuddering, especially during acceleration. 
• Handling issues: If you experience difficulty turning, a feeling of the vehicle pulling to one side, or stiff steering, the differential may need service. 
• Uneven tire wear: Check your tires for uneven wear patterns, which can be caused by a malfunctioning differential. 

Visual and olfactory signs

• Leaks: Look for red or dark fluid puddles or spots under the rear of your vehicle. 
• Burning smell: A burning or hot metal smell coming from under the vehicle can signal overheating due to low or dirty fluid. 
• Dirty fluid: If you can, check the fluid itself. It should be clean, not thick, dark, or contaminated. 

This video demonstrates how to check the differential fluid level: 39sLRMLeasingYouTube · Jan 18, 2024
What to do

• Check your owner's manual: Follow your vehicle's recommended maintenance schedule for the most accurate information. 
• Consult a mechanic: If you notice any of these signs, it's best to have a qualified mechanic inspect your differential to prevent potential damage. 

Is differential fluid a lifetime fluid?

However, as a general guideline, it is recommended to change the differential fluid every 30,000 to 60,000 miles.

How much does it cost to have differential fluid changed?

Changing differential fluid typically costs between $100 and $200 for a single differential at an independent shop. The price can increase to $200–$400 or more if both front and rear differentials need service, and you may pay more at a dealership. Costs vary based on location, vehicle, and labor rates. 
Cost breakdown

• Single differential: Approximately $100–$200 for one differential at an independent shop. 
• Front and rear differentials: Around $200–$400 for a full service on both differentials. 
• Dealerships: Often charge higher prices, with some quotes for a single differential reaching close to or over $200. 
• DIY: The cheapest option is to do it yourself, as fluid costs can be around $100 or less, not including tools and labor. 

Factors that influence the price

• Vehicle type: The make, model, and age of your vehicle can affect the price. 
• Location: Labor rates vary by geographic area. 
• Service provider: Independent repair shops generally have lower labor rates than dealerships. 
• Additional services: If other repairs are needed, such as replacing pinion seals, the cost will be higher. 

When to consider professional service

• If you have no experience: Changing differential fluid requires getting under the vehicle and can be messy, so professional service is recommended if you are not comfortable with this type of work. 
• If you need your vehicle's maintenance minder reset: Some modern vehicles have a maintenance minder that needs to be reset after the fluid change, which a shop can handle for you. 

What happens if you never change your differential fluid?

If you never change your differential fluid, it will break down over time, leading to contamination from metal particles and moisture, which will cause increased wear on the gears and bearings. This can result in noise, poor performance, and eventually, catastrophic failure where the differential seizes up completely, causing a complete loss of control. 
What happens to the fluid

• Breakdown: The fluid breaks down over time, losing its viscosity and protective additives.
• Contamination: It accumulates microscopic metal particles from wear on gears and bearings, which act like sandpaper and accelerate further wear.
• Moisture: Moisture and dirt can enter through the breather vent, causing corrosion and affecting the fluid's ability to lubricate. 

Symptoms of a problem

• Noise: A whirring, whining, or howling sound from the differential area.
• Vibrations: Unusual vibrations that get progressively worse.
• Discoloration: The fluid can appear dark brown, black, or even grey. 

Consequences of not changing the fluid

• Increased wear: The abrasive metal particles and lack of lubrication cause premature wear on the gears and bearings. 
• Heat: Without proper lubrication and cooling, the differential can overheat. 
• Failure: The gears and bearings will eventually wear out to the point of failure. 
• Catastrophic failure: In the worst-case scenario, the differential will seize up completely, causing the vehicle to come to a sudden stop and potentially leading to an accident. 

The bottom line
Changing the differential fluid is a necessary maintenance task, especially for rear- and all-wheel-drive vehicles. It's a preventative measure that can save you from costly repairs and dangerous failures down the road. Cars.com suggests that changing the fluid after the initial break-in period can also be beneficial to flush out initial metal shavings from assembly.