,## The differential fluid,,In short:This fluid is used only inoff-road cars and rear-wheel-drive cars.You may notice that you need to change it if you hear abuzzingnoise coming from the back of your A8 e when your car moves, that gets noisier when the speed increases.,This lubricant fluid is essential tokeep the differential in good shape.It prevents the system from wearing away and keeps its temperature stable. The differential is a set of gears thatcan only be found in rear-wheel-drive cars and off-road cars.This fluid is not used for front-wheel-drive cars because the differential is built into the transmission.,,## When should you change the differential fluid of your A8 e?,,In off-road cars: you need to change it every 25,000 to 40,000 miles (40,000 to 60,000 kilometers).,In light cars with rear-wheel drive: it’s recommended every 90,000 miles (150,000 kilometers).,You should always read theowner’s manualto check this information.,You maynoticethat you need to change it if you hear abuzzingnoise coming from the back of your car when your carmoves, and it gets noisier when the speed increases.,If for some reason you check the fluid and see that it is very dark or you can see moisture in it, you should also change it.,,## What differential fluid should you use?,,The differential fluid is characterized, just like manual transmission fluid, by itsSAE viscosityandAPI standards. You can generally find this information for your A8 e in theowner’s manual.,Forlight cars, the fluid that isgenerallyused is eitherSAE 75W-80 or 75W-90.Heavy cars usuallyneedSAE 75W-140.,A commonconsequenceof not using the recommended fluid is theoverexertion of the engine and the internal piecesof the differential, which generate more resistance to move forward.,Regarding the API standards, the fluid that is usually required is the GL-4 fluid. Newer cars may require GL-5.,,## What is the differential?,,The differential is the last set of gears that exists before the wheels. It is used to transmit the movement from one axis to another which is at 90°, and it allows one wheel to turn slower or faster than the other, whichimproves maneuverability. They may be really simple sets or high-spec sets.,In front-wheel-drive cars, this set is not used because the differential is built into the transmission. Inrear-wheel-drive cars this is a separate set, sometimes built into the back axis.,You can see a picture of the main set of clogs of the differential system below.,,## Related guides,,,## Audi A8 e problems: differential fluid,
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