Transmission Leak Inspection
What is a transmission, and why might it leak?
The transmission is responsible for receiving power from the engine, and sending that power to the driveshaft or axles so that your car goes the speed you want. An automatic transmission adjusts on its own to driving demands, and keeps the engine running in an optimum range for a given speed.
The transmission oil pan gasket is the most common source of a leak, but fluid may also escape from loose seals, damaged transmission lines or a cracked or punctured pan.
How does a transmission work?
Automatic transmissions use the force supplied by the engine to pump pressurized automatic transmission fluid through many components. As the pressure increases or decreases, different clutches or bands will get activated, and these determine which gear your car is in. The higher the gear, the easier it will be for your car to go faster.
There are several systems that can leak oil. Each fluid tends to be a different color, which can help to identify the leaking system.
Engine oil tends to be brown or black. It can be an amber color if it's new oil
Power steering fluid can be many colors: clear, brown, green or red
Automatic transmission fluid is reddish in color
Engine coolant is green, red, orange, or clear. It has a watery consistency different from oil
What are the symptoms related to a transmission leak?
If your transmission is leaking, it will typically result in an oil puddle on the pavement under your car. Automatic transmission fluid is typically colored red or green. You should take your vehicle in for a transmission inspection as soon as you notice a leak. If you don't see it in time or ignore it, you may eventually notice the engine revving when you're not accelerating the vehicle — this is called transmission slipping, and can happen when your car is low on transmission fluid.
Can I drive with a transmission leak?
Continuing driving with a transmission fluid leak is not recommended, as the leak may become worse while driving and it will be impossible to tell how much fluid you lose while in motion. For small leaks or seepage, the vehicle may be driven to the repair facility. However, a car with a moderate to large leak should not be driven. In addition to pouring transmission fluid on the ground, the vehicle may suffer transmission failure from lack of lubrication, also called oil starvation.
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When do transmission leaks occur?
Automatic transmission leaks are most common in high-mileage transmissions in poor condition due to neglected maintenance. Performing factory maintenance on schedule is the best way to help prevent transmission failure. The transmission oil pan gasket is the most common leak to find on a transmission, and this leak is addressed as part of the regular automatic transmission service. Since each manufacturer may set different service intervals, check this page or your owner's manual for information on your vehicle.
How are transmission leaks diagnosed?
If a transmission leak is suspected, the auto technician will perform an inspection on the transmission to reveal its source. Once the suspected part or parts have been resealed or replaced, the transmission will be inspected again to make sure the leak has stopped.
Fluid leaks tend to move in a downward and rearward direction. Therefore, oil leaking at the rear of the transmission may have originated at the front. One way a shop avoids misdiagnosing oil leaks is to use oil detection dye that helps to pinpoint the exact source of the leak.
How is a transmission leak fixed?
Fixing a transmission seal or gasket can be easy, or it can require disassembly of several components or even removing the transmission entirely. This can involve lowering the transmission, removing the transfer case or removing the exhaust to access the driveshaft. If significant fluid loss is noted, a transmission fluid drain and fill is recommended.
RepairPal recommendations for transmission leaks
We recommend against any products that claim to stop transmission fluid leaks. These products can create a blockage in fluid passages and clog transmission fluid filters. Either of these outcomes can lead to internal damage. You're better off getting the leak repaired the right way.