What damage can improper transmission fluid replacement cause to a vehicle?

Improper transmission fluid replacement (including selecting the wrong type, mixing different fluids, or improper operation) can cause a range of damage to a vehicle, from short-term performance degradation to long-term component failure.

What damage can improper transmission fluid replacement cause to a vehicle?

Improper transmission fluid replacement (including selecting the wrong type, mixing different fluids, or improper operation) can cause a range of damage to a vehicle, from short-term performance degradation to long-term component failure.

In the short term, improper viscosity or degraded additives can cause clutch/brake engagement issues, leading to increased gearshift jerkiness, oxidation, or debris blocking the oil passages, which can result in abnormal hydraulic system pressure causing gearshift lag or impact. Additionally, long-term use of substandard oil or failure to replace it can cause ‘pitting’ of components such as the planetary carrier and differential, shortening the transmission's lifespan.
Long-term use can ultimately result in irreparable damage to the transmission.

How can you determine if transmission fluid has deteriorated and needs replacement?

This is quite straightforward. Typically, you should assess the fluid's appearance, odour, and driving feel, combined with the fluid's condition and mileage/usage time.
First, observe the colour change. Normal transmission fluid should be clear and transparent, ranging from red, amber, or light yellow (some models may be light green, refer to the manual for specifics). If the fluid darkens, turns black, or becomes cloudy, it indicates oxidation and contamination with impurities.
Next, the smell. Normal transmission fluid should only have a faint oil smell. If there is a burnt smell or a pungent odour, it may indicate clutch plate/brake band slippage or contamination with other chemical.

Finally, the driving experience. The primary functions of transmission fluid are lubrication, cooling, and power transmission. If you experience gearshift jerks/delays/power loss/sluggish acceleration/ abnormal noise, or unusual sounds during cold starts, these are warning signs from the transmission that require special attention.

If you are unable to determine the cause yourself, we recommend visiting a 4S store or consulting a TERZO professional to avoid damaging the transmission due to misjudgment.