Differential Fluid: What It Is And How To Change It

Failing to Properly Service A Differential Can Be A Costly Mistake.

While front-wheel drive has become very common since the 1980s, there are still plenty of modern vehicles (as well as classics) that feature rear, four, or all-wheel drive. On these vehicles, the transmission is connected to the drive axles with a driveshaft, and the engine’s torque is distributed across the axle (to both wheels) through a set of gears called the differential. 

What Is Differential Fluid Service?

Just like the engine, transmission, and transfer case, the differential is filled with fluid to properly lubricate the gears, and after time, the fluid breaks down and loses its viscosity, which can lead to the axle’s internal gears being damaged. For this reason, the differential fluid must be changed regularly and at specific mileage intervals for proper maintenance. 

Changing the differential fluid is an easy job that usually consists of removing the differential cover to drain the fluid, reinstalling the cover, and then refilling the differential. This service can also be referred to as the drive axle assembly drain and refill.

When Should You Change Differential Fluid?

Drive axles should be serviced as part of a routine maintenance schedule, and depending on the automaker, differential fluid services are usually suggested at around 30,000 to 60,000 miles. 

The easiest way to tell whether you need to perform a differential fluid change on your vehicle is to remove the fill plug and inspect the quality and level of the fluid. If the fluid is dark, milky, or extremely low, you should perform this service as soon as possible to prevent any damage (or further damage) to the gears. Also, if differential fluid is leaking from the cover, the pinion seal, or the axle seals, you should repair these leaks, which requires the differential to be serviced. 

Get the FIXD Sensor and free app today for a custom maintenance schedule based on your make, model, and mileage to know when it’s time for a differential fluid change on your specific car.

Can I Change My Differential Fluid Myself?

On most trucks and SUVs, performing a differential fluid change is an easy job, but on some vehicles, this maintenance item is a little trickier due to suspension components being in the way. If you own a vehicle that makes it easy, this DIY job will save you around $80 based on the average cost for a differential fluid change.

Most of the time, the cover needs to be removed for the fluid to be drained, and then you need to clean the surfaces on both the axle and the differential cover. Then apply a recommended sealer (usually applied from a tube) and then reinstall the cover. Some axles have a drain plug that can be removed in lieu of removing the cover. 

To fill the differential, make sure you’re using the proper oil viscosity for your differential and pump it into the axle until the fluid reaches the top of the fill hole and starts coming back out.

Conclusion

While oil changes, tire rotations, and transmission services are the most well-known types of maintenance you can perform on your car, don’t forget about servicing the differential(s) if you own a rear-, four- or all-wheel vehicle such as a pickup truck or SUV.  Whether you do it yourself or take it to a professional shop, this scheduled maintenance item should be a top priority to keep your vehicle on the road.