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Many drivers don’t even know what a differential is, because it’s one of the least common spoken about parts of a car. However, all cars have cogwheels which may be found on the rear or front side of the car, or even on both ends. Cars with a front differential and a built-in transaxle use different oil from cars with a rear differential. They need fully synthetic oil like SAE75 while rear cogwheels need thicker oil like SAE90.
Differential functions
Now you naturally wonder what the cogwheel’s purpose is in a car. They are most importantly needed while cars turn curves. When a car turns a corner, the outside wheel generally covers more ground than the wheel on the inside of the turn. Though there’s not much of a variance, as cars are precision vehicles, it is enough to lead to eventual huge damage. This is where the cogwheel comes into play, by compensating for the difference. It’s also why the oil is thick and dense, to keep the differential lubricated while compensating turns.
The gear fluid helps by lubricating the pinion and ring gears which transfer power from the driveshaft to wheel axles. It also keeps the car’s moving parts with the limited-slip cogwheel assembly healthy.So generally, like other oils, gear fluid is needed to both cool and lubricate cogwheels. Its absence only leads to it eventually overheating and burning out because of the repeated contact and friction between metal parts.
How often to change gear oil
Most car manufacturers suggest changing gear fluid every 30,000 to 60,000 miles. This time interval, however, is different for rear and front oils. In case of rear oils, it has to be changed every 30,000 to 50,000 miles. In the case of the front, it’s important that you change it a bit earlier, between 25,000 to 30,000 miles. Whatever the situation, unless the fluid has been contaminated with some water, it is always better to check the user’s manual to find out the car’s exact mileage amount, and when it’s better to change the oil.
It is always better to have licensed mechanics change both rear and front differential oils because this is a messy job. The fluid has to be first properly disposed of. Then all the parts in the cogwheel housing have to be wiped down to ensure no contaminants from the old fluid get transferred to the new oil. Based on the condition of the oil and the cogwheel, you may also need a new gasket. Lastly, the most important reason to leave this job to the professionals is that the car has to be lifted to change the oil. The reason for this is that the cogwheel is located under the car.
Importance of changing gear oil on time
Like any other oil in the car, the main reason for changing gear oil is the frequent contact between metal parts in the car leads to its wear and tear. This, in turn, creates a lot of friction which will weaken gears to lead to possible failure. The best way to keep cogwheels working in optimal condition, and to avoid unnecessary expensive repairs, it is better to follow your car manufacturer’s recommended interval for changing gear oil and change it.
How to check differential oil
Checking gear fluid levels in light trucks is actually comparatively easier when compared to cars. Though you may have to spend some time and effort checking the oil, it is worth it. you eventually end up preventing lots of inconvenience and potential problems like gear failures and bad bearings. It is while checking the fluid that you have to look for signs of wetness and leaks around both axle seals and the pinion gear seal. Leaks around the gear cover also indicate low differential fluid levels.
If it’s your new car, check the oil level as soon as you receive your car. This is because many car manufacturers ship their cars with minimal differential fluids, to avoid leakages in transit. In this case, it is the dealer’s responsibility to inspect the car and top up the fluid as required before selling it.
The procedure
As mentioned above, the car has to be jacked up to check the gear oil level and make sure you wear protective eyewear and gloves before starting the check. Look for the oil fill plug that’s usually on the front part of the differential, near the pinion gear flange. Cogwheels that have locking carriers have a tag informing the need of using a special fluid or additive during service. The gear cover plate behind the housing also has level inspection plugs.
Remove the fill port plug using a tool like a 3/8 drive extension and then use a small wire or your little finger to check the fluid level. If it’s full, then the oil should be just below the plug hole’s level. Reinsert the plug in case the oil pours out once the plug is removed. A wet wire means the gear oils levels are okay. It’s very important that you do not turn the drive shaft or rear wheels while checking the oil levels because it could injure your finger. And if the wire or your finger doesn’t have any oil on it, it means the differential fluid level is low.
The low fluid levels mean it is time to fill it up. Most gear oil quarts come with a small nozzle and hose you can use to easily pour the oil into the service port. Keep filling up till the oil spills out of the service port.
All you have to do is reinsert your little finger to double-check and reconfirm. It’s when all this is done that you have to manually reinsert the differential fill plug to avoid possible cross threading, and then tighten it to 15-foot pounds of torque. You can use a shop towel to wipe off any excess gear oil after tightening the port. It is always better to periodically perform a differential fluid service and check to ensure there’s enough oil for its proper functioning.
Last update on 2020-04-04 / Affiliate links / Images from Amazon Product Advertising API
