Q: Why would transmission fluid leak?

asked by on

Why would transmission fluid leak?

First, we should acknowledge that the transmission, whether automatic or manual, is actually designed to hold the fluid without leaking. However, there are many factors which can cause a transmission to leak.

Drying or hardening seals can cause leaks. Failing pressure lines in an automatic transmission system can crack, dry rot, or be damaged by something hitting them while driving. Automatic transmission systems use a cooler unit usually included in the radiator and these can fail due to vibration or corrosion of the housing over time. If an external or additional cooler is used, it is often in front of the radiator and condenser and subject to damage from debris on the highway. Areas known for leaks include faulty components, misaligned or faulty gaskets, and loose drain plugs or lines. Temperature changes and the difference in metal and gasket types can lead to leaks over time. Modern electronically-controlled transmissions have electrical connections that go into the transmission case or through the transmission pan. I have seen porous casting in the past causing internal or external leaks as well. In older vehicles that used vacuum modulator valves to control shift points, the diaphragm would sometimes rupture, causing the fluid to be leaked into the engine through the vacuum line that was used to signal or control the valves’ operation.

As with any system, a regular check of fluid level and condition will help to avoid costly repairs. If you suspect a leak, have the vehicle inspected as soon as possible. Transmission fluid serves several purposes. It acts as the pressure agent to actuate clutch packs to control the different gear ranges. It also lubricates and cools the transmission. Loss of fluid causes aeration of the fluid, known as cavitation. Like all hydraulic systems, the transmission system depends on the ability of the fluids to not compress if the level get low. If they get air bound, parts can slip and damage will ensue. Keeping the level full and the fluid cool will extend the life of the transmission.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Why would transmission fluid leak?

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Car slams into gear after having transmission flushed

Sometimes, on older and/or high mileage transmissions, a fluid flush can be detrimental. The old fluid (which is full of friction material from the transmission clutches) is all that is holding the transmission together. However, this may not be the...

Q: My car jumps when I go from brakes to gas

Hi There, It sounds like your car may be low on transmission fluid. Automatic transmissions use pressurized hydraulic fluid (Transmission fluid) to change gears. Every time a gear change is required, the car's computer activates a transmission solenoid, which directs...

Q: when I'm driving down the road about 45 and let off the gas my rpm drops and the car act like it's in nuetral. at 2500 it goes

It sounds like what you are experiencing is transmission related. I would want to check the automatic transmission fluid (ATF) level and condition. It may be low on fluid. You may smell burnt fluid if the trans has been slipping....

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.