Transmission fluid leakage: causes and effects

Transmission fluid leak can degenerate to serious transmission faults or total damage if the leak is not fixed immediately.


Have you noticed a transmission fluid leakage and you don't know whether you can manage the car to your next destination or simply park the car to fix it first?

Transmission oil leakage can be minor or major but not fixing it will eventually lead to destruction of the transmission.

Even if the leakage is minor, it should be fixed immediately.



1. Leak in oil pan due to impact with rocks, curbs and so on..

2. Leak in cooler line. The cooler line that routes the oil from the transmission to the oil cooler can develop leaks.

3. Leak in transmission oil cooler itself. This is possible when there is internal rupture in the oil cooler itself. When this happens, the transmission oil might find its way into the cooling system and you will notice that the coolant will become milky, oily, muddy or brownish.

4. Leak in radiator. While some cars use the cooling system radiator to exchange heat between the transmission oil and coolant, some other cars have dedicated radiators to cool the transmission oil. Either of them can leak.

5. Worn or broken seals can cause leakage. This is because over time, these seals begin to deteriorate, allowing the oil to leak.

6. Leakage at the torque converter as a result of cracked torque converter housing can cause oil leakage into the transmission itself.

Not changing the transmission fluid early enough can cause metal particles and clutch materials to saturate in the oil. These materials cause premature wear of seals.

An over filled transmission can cause seals to break or vent fluid through the dipstick hole. This is a common cause of transmission fluid leakage.

Transmission pan gasket: Oil can leak here if the gasket is not properly fixed or it has normally worn out.



1. When the fluid level becomes low, the transmission does not operate normally anymore and might make the car owner to become stranded.

2. A low fluid level as a result of leakage will reduce lubrication in the transmission and will increase friction and hence cause premature damage to the transmission.

3. A low fluid level due to leakage will reduce the cooling efficiency in the transmission because there won't be enough fluid to remove heat.

Transmission fluid level should be checked as often as possible. Procedures for checking transmission fluid level is here: procedure for checking transmission fluid level

Also check transmission fluid quality by checking the color because a low transmission fluid will cause the fluid to overheat and burn. That causes its color to change from clear/transparent to opaque and dark color.

It's always better to prevent transmission fluid leak than repair it by changing the oil when it is due for change and installing belly plate for the engine/transmission.

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