1、 Precautions for gearbox oil inspection
The premise of inspection should be accurate
Oil temperature requirement: Most automatic transmissions (AT/DCT/CVT) need to heat the oil to 40 ℃ -60 ℃ (idle for 5-10 minutes without turning off the engine), at which point the oil is at normal working viscosity and the liquid level measurement is most accurate; The manual gearbox can be inspected for cold driving.
Parking position: It must be parked on a level surface, otherwise the liquid level may deviate, leading to misjudgment.
Differences in inspection methods for different gearboxes
Manual transmission (MT): Find the oil level check bolt on the side of the transmission, and if the oil just flows out of the bolt hole after unscrewing, or if the oil can be felt (0-5mm away from the hole), the liquid level is normal; If there is no oil flowing out, it indicates insufficient.
Automatic transmission (AT): Check the oil dipstick (some new models do not have a dipstick, special equipment is required), remove the dipstick and wipe it clean before inserting it, and then remove it again to observe the oil level - it should be within the * * "HOT" (hot state) scale range of the dipstick, and neither too high nor too low is acceptable.
Non dipstick models (some AT/DCT/CVT): It is necessary to go to a professional repair shop, use a diagnostic computer to read the oil temperature, and then check the liquid level through the oil drain bolt or special detection hole, which is difficult for individuals to operate accurately.
Oil state judgment
Normal state: The oil is transparent or light yellow, with no odor or obvious metal debris.
Abnormal state: The oil turns black, has a burnt smell (high-temperature oxidation), emulsifies and turns white (mixed with water), contains metal particles (internal wear). If any of the above situations occur, the oil should be replaced immediately and the gearbox should be checked for faults.
2、 Precautions for gearbox oil replacement
The selection of oil must not be wrong
Strictly match the transmission type: AT special oil for AT, CVT special oil for CVT, DCT special oil for wet DCT, and gear oil for dry DCT and MT. Different types of fluids cannot be mixed, otherwise it will cause gear shifting jerks, component corrosion, and even gearbox scrapping.
Reference manufacturer specifications: Prioritize the oil specifications specified in the vehicle maintenance manual (such as Dexron VI and Mercon LV standards for AT oil), and avoid using inferior or non-standard oil.
Selection of replacement method
Gravity oil change: simple operation and low cost. The old oil is drained through the oil drain bolt and new oil is added. The disadvantage is that only 40% -60% of the old oil can be replaced, and residual oil will affect the performance of the new oil. Suitable for vehicles with good oil condition and only regular maintenance.
Circulating machine oil change: Using specialized equipment to circulate and replace new and old oil can replace 80% -95% of the old oil, with better results but higher costs and fuel consumption. Suitable for vehicles with severely deteriorated oil and high mileage.
Attention: It is not recommended to use a circulation machine to change oil in some gearboxes (such as some CVTs and dual clutch transmissions) to avoid impacting internal precision components. It is necessary to follow the manufacturer's requirements.
Key points of operation after replacement
The filling amount should be precise: first fill the basic amount according to the manual standard, switch to all gears after starting the engine (stay in each gear for 2-3 seconds), then check the fluid level and gradually fill it to the standard scale. Avoid overfilling (which can cause high oil temperature and oil seal leakage).
Test drive inspection: After replacement, idle for 5 minutes, then drive on the road for 10-15 kilometers to feel whether the gear shift is smooth, observe for oil leakage, abnormal noise, and the fault light is on.
Other details
When replacing the oil, it is recommended to check or replace the transmission oil filter element and sealing gasket simultaneously. Blockage of the filter element will affect the oil circulation, and aging of the gasket can easily lead to oil leakage.
Avoid disassembling the oil drain bolt when the gearbox is hot to prevent scalding from hot oil splashing.