How to replace the differential output shaft seal

Differential outlet seals prevent fluid from leaking out of the differential, which can cause the differential to overheat and damage the vehicle.

Whether your car is front wheel drive, rear wheel drive or all wheel drive, a common component that all cars have is the differential. The differential is a housing that contains the gear train of the axle and is connected to the drive shaft to transfer power to the drive axle. Each differential, either front or rear, or both in the case of four-wheel drive vehicles, has an input and output shaft to supply and distribute power. Each shaft has a rubber or hard plastic seal that prevents transmission oil from leaking as well as protecting the gearbox's internal components from contamination from external debris. In many cases, when a differential is found to be leaking oil, it is caused by a damaged differential output seal or axle seal.

Like any other seal or gasket, the output differential seal is subject to wear due to overexposure to the elements, aging, and exposure to gear oil, which is very thick and contains corrosive chemicals that will eventually dry out the seal. When the seal dries, it is prone to cracking. This creates microscopic holes between the differential housing and the output shaft cover. Under load, the gear oil builds up pressure and can leak out of the seal holes and onto the ground.

Over time, due to the above facts, the differential output shaft seal may leak, resulting in fluid leakage. When this happens, the differential is not lubricated, so the bearings and gears can overheat. If these parts start to overheat, it can cause serious damage to the differential, which can put the car out of action until the differential is repaired.

Typically, the outlet seal will leak more while the vehicle is in motion; especially when axles attached to the differential are driven by gears inside the differential. As oil leaks, the lubricity inside the differential deteriorates, which can cause significant damage to gears, axles, and components inside the housing.

Like any mechanical component that loses lubrication, when the outlet seal leaks fluid, there are a number of warning signs or symptoms that should alert the driver to a problem. Some of the most common signs of a bad or broken differential output shaft seal include:

You notice fluid on the outside of the diff and axle: The most common sign that the output shaft seal is damaged is when you notice fluid covering the area where the output shaft connects the axle to the differential. Typically, a leak will start at one part of the seal and slowly expand to infiltrate the gear oil through the entire seal. When this happens, the fluid level inside the differential housing drops rapidly; which may damage components.

Creaking sounds from under the car when cornering: If transmission fluid leaks, the metal components inside the differential will overheat and may rub against each other. When this happens, you will usually hear a grinding sound coming from under the car if you turn left or right. If you notice this type of sound, it means that the metal parts are actually rubbing; causing significant damage.

Smell of burnt gear oil: Gear oil is much thicker in viscosity than engine oil. When it starts to leak from the output shaft seal, it can get into the exhaust pipes under the vehicle. This is usually the case with front differentials on XNUMXWD or XNUMXWD vehicles. If it leaks onto the exhaust, it usually burns as smoke, but if the leak is significant enough, it can ignite.

Any of the above symptoms can be avoided with regular maintenance and repairs. Most car manufacturers recommend draining the differential oil and replacing the input and output seals every 50,000 miles. In fact, most output and input shaft oil seal leaks occur after the 100,000 mile mark, or after 5 years of wear.

For the purposes of this article, we will focus on the best recommended methods for removing the old differential output shaft seal and replacing it with a new inner seal. However, each vehicle has unique steps to complete this process. Therefore, we will focus on general instructions for removing and replacing the seal on most vehicles. For detailed instructions on how to complete this process, please refer to your vehicle's service manual or contact a differential specialist who can assist you with this task.

Part 1 of 3: Causes of Differential Output Shaft Seal Failure

Depending on the location of the differential, i.e. front wheel drive or rear differential, leakage from the output shaft seal can be caused by different circumstances. On front wheel drive vehicles, the transmission is usually attached to a single housing differential often referred to as the transmission, while on rear wheel drive vehicles the differential is driven by a drive shaft attached to the transmission.

The outlet seals on front wheel drive vehicles can be damaged due to excessive heat, hydraulic fluid deterioration, or excessive pressure. Seal failure can also occur due to exposure to the elements, age, or simple wear and tear. In rear wheel differentials, the output seals are usually damaged due to age or over-exposure to the elements. They are supposed to be serviced every 50,000 miles, but most car and truck owners don't perform this service.

In most cases, a slow leak from the differential output seal will not cause driving problems. However, since oil reserves cannot be replenished; without physically adding it to the diff, it could eventually cause serious damage to the internal components inside. When the oil flows for a significant period of time, most of the symptoms appear, such as:

• Screeching noise from under car when turning
• Smell of burnt gear oil
• Knocking sound coming from car when accelerating forward

In each of the above cases, the damage is done to the internal components inside the differential.

• A warningA: The job of replacing a differential output shaft can be very difficult depending on the type of vehicle you have. It is always recommended to review the manufacturer's service manual in its entirety before attempting this job. As we stated above, the instructions below are the general steps for replacing the output seal of a typical differential. If you are not comfortable with this job, always contact an ASE certified mechanic.

Part 2 of 3: Preparing the Vehicle for Replacing the Differential Output Shaft Seal

According to most service manuals, the job of replacing the differential output shaft seal can take 3 to 5 hours. On some vehicles that have solid rear casings, the inner seal is called an axle seal, which is usually located on rear wheel drive vehicles and inside the vehicle's rear hub. To remove this type of output seal, you will have to remove the differential case and disconnect the axle from the inside.

On front wheel drive vehicles, the outlet seal is also commonly referred to as a CV joint seal. It should not be confused with the CV joint boot, which covers the CV joint housing. To remove a conventional output shaft seal on a front drive differential, you will need to remove some of the brake hardware, and in many cases remove the struts and other front components.

In general, the materials you will need to remove and replace the seal; after removal of auxiliary components will include the following:

Necessary materials

• Maybe brake cleaner
• Clean shop rag
• Drip tray
• Limited slip additive (if you have a limited slip differential)
• Seal removal tool and installation tool
• Flat and Phillips screwdrivers
• Socket set and ratchet
• Replacing the differential output seal
• Rear oil change
• Scraper for plastic gasket
• Wrench

After gathering all of these materials and reading the instructions in your service manual, you should be ready to get the job done.

Part 3 of 3: Steps to Replace the Differential Gasket

According to most manufacturers, this job should be done within a few hours, especially if you've got all the materials and a spare gasket. While this job does not require you to disconnect the battery cables, it is always a good idea to complete this step before working on the vehicle.

Step 1: Jack up the car: To remove any output differential seal (front or rear of the vehicle), you will have to remove the wheels and tires to get the axle out of the differential. That's why you will need to raise the car on a hydraulic lift or put the car on jacks. It's always best to use a hydraulic lift if you have one.

Step 2: Remove the wheel: Any time you replace a leaking output shaft seal, you will first need to remove the wheels and tires. Using an impact wrench or torx wrench, remove the wheel and tire from the axle that has the leaking differential output shaft, then set the wheel aside for now.

Step 3: Preparing the axle for removal: In most cases, you will have to remove the axle from the differential in order to replace the outer differential seal. In this step, you will follow the instructions in the service manual to remove the following components.

• spindle nut
• Wheel bearings
• Stopping support
• Emergency brake (if on the rear axle)
• Shock absorbers
• Tie rod ends

On front wheel drive vehicles, you will also need to remove the steering components and other front suspension parts.

• AttentionA: Due to the fact that all vehicles are different and have different attachments, it is very important to follow the instructions in your service manual or have this job done by an ASE certified mechanic. A good rule of thumb is to record each removal step, as installation after replacing a broken seal will be done in the reverse order of removal.

Step 4: Remove the axle: Once all fasteners have been removed so you can remove the axle from the differential, pull the axle out of the differential. In most cases, this does not require a special tool to remove the axle from the vehicle. As you can see from the image, you can see how the super arms are still attached to the axle. This greatly simplifies the installation of this part after replacing a damaged seal.

The image above shows the bolts that attach the CV joint to the front differential on a standard front wheel drive vehicle. You will also have to remove these bolts to remove the axle from the differential. This step is not typical for rear wheel drive vehicles. As repeatedly stated above, always refer to the service manual for exact instructions.

Step 5: Removing the Damaged Outer Differential Seal: When the axle is removed from the differential, you will be able to see the output seal. Before removing a broken seal, it is recommended to stuff the inside of the differential with a clean rag or disposable wipes. This will protect the inside of the differential from attack by the elements or contamination.

To remove this seal, it is best to use the seal removal tool shown in the image above or a large flat blade screwdriver to slowly remove the seal from its body. It is important to remember that it is important not to scratch the inside of the differential.

Completely remove the seal, but leave it to match the replacement part you purchased before attempting to install a new seal.

Step 6: Clean differential inner seal housing and axle housing: The most common source of new leaks resulting from recent outer seal replacement work is due to a lack of cleaning by a mechanic. It is important to remember that the two parts that are joined together must be clean and free of debris in order for the seal to do its job properly.

• Using a clean rag, spray some brake cleaner on the rag and clean the inside of the differential first. Be sure to remove any excess sealing material that may have broken during removal.

• Then clean the axle fitting inserted into the differential gearbox. Spray a generous amount of brake fluid onto the male fitting and axle gear portion and remove all grease and debris.

In the next step, you will install a new output differential seal. The above tool is for installing the seal. You can find them at Harbor Freight or at a hardware store. They are very good for installing seals in differentials, gearboxes and almost any input or output shaft.

Step 7: Install New Secondary Differential Seal: Using the tool shown above, you will install the new seal following these guidelines.

* Remove the rag or paper towel you put inside the differential.

• Using fresh gear oil, apply a thin coat around the entire circumference of the housing where the seal will be installed. This will help the seal to sit straight.

• Install the differential seal

• Place the flush seal tool on the new seal.

• Use a hammer to strike the end of the installation tool until the seal snaps into place. In most cases, you will actually feel the seal "pop" when it is properly installed.

Step 8: Lubricate the ends of the axles and install them back into the differential: Using fresh gear oil, liberally lubricate the axle gear end that will attach to the internal gears inside the differential. Carefully place the axle into the gears, making sure they are aligned straight and not forced. As you can see in the image below, make sure you align the axis correctly. Many tend to tag the hub axle when removed as a resource.

Tighten all bolts and fasteners that you had to remove in the previous steps in reverse order of removal before moving on to the last steps.

Step 8: Fill differential with fluid: After installing the axle, as well as all suspension and steering equipment, fill the differential with fluid. To complete this step, please refer to your service manual as each vehicle has different procedures for this step.

Step 9: Reinstall the wheel and tire: Be sure to install the wheel and tire and tighten the lug nuts to the recommended torque.

Step 10: Lower the vehicle and re-tighten all bolts on the differential.. Once you've completed the process of replacing the differential output seal, you may want to consider replacing another one on the same axle (especially if it's front wheel drive).

Some other components on front wheel drive vehicles that you should remove and replace during this service include CV boots; as they usually break at the same time as the outlet seal on front wheel drive vehicles. After replacing this component, a good 15 mile road test is recommended. After completing the check, crawl under the vehicle and inspect the differential case to ensure there are no fresh fluid leaks.

When you complete this task, the output differential seal repair will be complete. If you have gone through the steps in this article and are unsure about completing this project, or if you need an additional team of professionals to help solve the problem, contact AvtoTachki and one of our local ASE certified mechanics will be happy to help you replace the differential . outlet seal.