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Transmission Fluid Leak

Abhijit Naik
Of the most common car problems that you are likely to face in the long run, one of the most serious problems would be transmission fluid leak. Going through these details will help you understand why this problem should not be taken lightly.
Transmission fluid lubricates various moving components of the transmission system in a vehicle, and keeps problems like corrosion and overheating at bay. While vehicles with manual transmission use gear oil or engine oil as lubricant, those with automatic transmission use automatic transmission fluid.

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Regardless of which transmission your vehicle is equipped with, the problem of transmission fluid leak is bound to bother you over the course of time.

What Causes the Transmission Fluid to Leak

Any damage to the vehicle's transmission case can lead to transmission fluid leak, but the chances of this are very rare. (If at all, it is most likely to happen when you are driving on rough surface with plenty of stones or rocks).
On the contrary, the chances of fluid leak resulting from loose transmission pan or damaged seals exist in plenty, and are a lot more serious as they often go unnoticed.
People often complain that they started experiencing transmission leak only after they got the transmission fluid filter changed. This usually happens when the transmission bolts are not fixed properly after changing the filter. It is important to tighten these bolts as failing to do so can result in loose transmission pan, which, in turn, can cause the transmission fluid to leak out.
Transmission fluid is circulated by the transmission fluid line and a torque converter, and damage to these components -- usually in form of cracks -- invariably ends up in fluid leak.
Though the transmission fluid line is usually made of steel or aluminum, continuous exposure to heat and debris makes it vulnerable to damage. A damaged torque converter can also trigger fluid leak, though the chances of that are very rare.
As in case of transmission fluid line and torque converter, damaged transmission seals are also known to trigger transmission fluid leak. Even these seals are made from metal or rubber, but being exposed to extreme temperature all the time, even they are vulnerable to continuous wear and tear -- and resultant damage.

The Consequences of Low Transmission Fluid

Unattended leak can eventually result in low transmission fluid which can damage the transmission system, and therefore has to be fixed the earliest. If the moving components of the transmission are not properly lubricated, they are bound to wear out faster.
Furthermore, if you use automatic transmission fluid -- which doubles up as coolant -- then the damage induced will be even greater. Continuous friction and overheating will eventually result in corrosion of transmission parts, and such damage is bound to come heavy on your pockets.

Diagnosing Transmission Leak

You can determine whether your vehicle is losing transmission fluid by observing the vehicle and your surroundings. One of the most common (and easy-to-identify) symptoms of fluid leak is engine overheating. If you experience it rather frequently, you should check all the places from where fluid can leak - including the drain plug and various joints.
If there is a fluid leak, you are bound to see spots or a puddle of oil beneath your car - i.e. on the garage floor or along your driveway. An easy way to ascertain whether any leak exists is to lay an old newspaper beneath the car.
(If possible you can switch newspaper with aluminum foil, as the latter will make it easier for you to determine how much oil you are losing.) You should ideally carry out this test when the engine is warm.
You may also use a dipstick to find out whether there is a fluid leak. If you are losing fluid, you will notice that the fluid level in the vehicle drops frequently. (It will also help you figure out whether the transmission fluid has gone bad, and needs to be changed.) If there is any fluid leak, the engine will be smeared with the fluid and a closer look will help you confirm the same.
You need to make sure that the fluid that you are losing is transmission fluid, and not some other fluid used in the vehicle. Your vehicle uses several different types of fluids. Misdiagnosing certain fluid leaks -- like brake oil leak -- can be disastrous for the vehicle as well as yourself.

How to Fix this Problem

Before you initiate the repair, you need to asses the seriousness of the problem. Depending on the extent of damage and amount of fluid that is being lost, you will have to decide whether to repair it on your own or go to a car workshop. If the problem is minor, you can use a stop leak solution to seal the fluid leak.
Experts seem to be divided over the use of such stop leak products; some experts recommend these additives, while others feel it is a futile exercise as the problem will surface again and again.
If it's a major leak you will have to take the car to a workshop to get it fixed. In this case, you can use a stop leak solution as a temporary arrangement. If you intend to deal with this problem once and for all -- which you ideally should -- you will have to seek professional help.
At the workshop, the professionals will asses the damage caused to the transmission and initiate its repair. Based on the extent of damage, you might have to replace the worn out part of the transmission. Welding could be an option if the oil pan is damaged, but some experts are of the opinion that replacing it is a better bet.
The cost on fixing transmission fluid leak will be determined by nature of the problem. Use of stop leak additive may cost around US$15-25, but is better to spend that amount in the initial stage when the damage is not severe. If not fixed in time, it can lead to major transmission problems, and cost you a fortune, at times in excess of US$1000, on repairs.