Can I Put Brake Fluid in my Transmission to Stop the Fluid from Leaking?

It is not a good idea to add brake fluid to your transmission in the hopes of stopping fluid leaks. The mixing of brake fluid with transmission fluid will cause many problems and quite possibly ruin the transmission. The best course of action is to replace the leaking seals, O-rings, and gaskets.

What happens if I put brake fluid in my transmission?

The short term effect will be the brake fluid will cause the seals to swell and stop the fluid leak for a short time.

The long term effect will be the transmission will be destroyed by the effects of the brake fluid. The brake fluid will ruin the seals, destroy the friction material on the clutch packs causing extreme transmission slippage which will, in turn, ruin the transmission.

The mixing of brake fluid with transmission fluid results in a milky, gummy mess that will cause damage of the transmission resulting in failure. At this point, the remedy is repair or replace, with neither one being an inexpensive solution.

What can I put in my transmission to stop a leak?

There is no “magic potion” that will stop transmission fluid leaks. The whole concept is marketing hype and only delays the inevitable of replacing seals and O-rings to stop fluid leaks. Take the pan off the transmission and replace the seals and O-rings that are exposed. At the same time you can replace the pan gasket with a new one.

Is transmission fluid compatible with brake fluid?

The two fluids are dissimilar, with transmission fluid being oil based and the brake fluid being a water soluble product. The brake fluid is extremely hygroscopic (attracts moisture). Oil and water do not mix well and will eventually turn into a milky gummy mess that will cause all kinds of problems in your automatic transmission.

Can you seal a transmission fluid leak?

The only successful remedy to stop a transmission fluid leak is the replacement of the leaking seal or O-ring. This can be accomplished without transmission removal, most of the time.

Seals and O-rings that leak to the outside can be accessed by removing the transmission oil pan and then removing and replacing the offending seal or O-ring. An exception to this is the front seal which requires transmission removal for access.

A few transmission parts may need to be removed to gain access to the leaking seal or O-ring. The shifter shaft seal is a common leak point and does require removal of the shifter shaft to do a proper job of removal and replacement.

The dipstick tube also requires removal for replacement of its seal or O-ring.

Many modern autos no longer have a dipstick, making it extremely difficult to add fluid to compensate for transmission fluid loss.

These vehicles will need seal or O-ring replacement to stop any leaks, thus avoiding transmission failure.

How do you temporarily fix a slipping transmission?

The temporary fix is to be sure the transmission fluid level is correct. Add fluid as needed to maintain the proper fill level. Look in your owner’s manual for the correct procedure for checking transmission fluid fill level. The other remedies require transmission removal and repair. This is usually a complete overhaul with new seals and clutch packs.

Can you substitute anything for transmission fluid?

There is no substitute for transmission fluid. Each vehicle brand can have a different fluid specification requirement due to the materials used in the transmission such as seals, O-rings, and clutch packs.

There are multiple types of transmission fluid being marketed today. Check your owner’s manual for the recommended type.

A few examples of fluid types:

Type A for transmissions through the 1960s (except Ford)

Type F for Ford transmissions through the 1960s

Dexron for vehicles 1960’s to 1980s

Mercon for Ford vehicle to 1980s

DexronII for vehicles after 1980s

MerconII for Ford vehicles after 1980s

Chrysler and Jeep developed their own individual fluids after the 1980s

Now, it seems each manufacturer has their own brand-specific transmission fluid that must be used for proper performance and longevity. Check your owner’s manual for the specific recommended fluid to use.

How do you stop a transmission front seal from leaking?

To stop a transmission front seal from leaking, you replace it with a new seal. This repair requires removal of transmission to gain access to the front seal. It is a labor intensive job and does require some specialty tools. A vehicle service manual would help greatly in this endeavor.

A front seal retains pressurized fluid from the transmission pump and must be in very good condition to meet the needs of this job.

Any leaks from the front of the transmission require immediate repair as these seals do not heal themselves.

What fluid stops transmission from slipping?

Once a transmission is slipping, the remedy is repairing the faulty components that are causing the slippage. There is no “pour in” slippage fix.

What causes a transmission to leak transmission fluid?

Transmissions leak their fluid due to faulty seals or O-rings, or a compromised pan gasket. Transmissions have a vent that can become plugged, causing the transmission to pressurize internally and thus force fluid out through weak seals.

The transmission pan gasket can lose its ability to seal and will need to be replaced. Never use RTV silicone to seal a transmission pan. Small bits of the silicone can break loose and migrate into the valve body and hang a valve with catastrophic consequences.

Is transmission fluid different from brake fluid?

The two fluids are dissimilar, with transmission fluid being oil based and the brake fluid being a water soluble product. Oil and water do not mix well and will eventually turn into a milky gummy mess that will cause all kinds of problems in your automatic transmission.

Is power steering fluid the same as transmission fluid?

Power steering fluid and transmission fluid are similar, but the transmission fluid has additives to prevent foaming, protect seals, and provide the correct friction coefficient for the transmission to work properly. Transmission fluid contains a dye that also helps keep seals from hardening.

The anti-foaming agent in power steering fluid is quite different from the transmission fluid additive. Power steering fluid does not contain a dye but is clear.

Can I use DOT4 brake fluid as clutch fluid?

Check your owner’s manual for the correct clutch fluid for your auto. Many do use DOT4 fluid as the original equipment recommendation. The majority of autos use DOT3 for clutch fluid. Some brands of vehicles share the same fluid reservoir jointly with the clutch and brake master cylinders.

Why is my transmission leaking when parked?

Your transmission is leaking because of bad seal(s) or O-rings, or a leaky pan gasket. One item to check is the transmission vent. It can become clogged and cause the internal transmission case to become pressurized, forcing fluid out around weak seals.

Where are the most common places for a transmission to leak?

A transmission will leak around the output shaft seal, through the pan gasket, around the shifter-shaft seal, dipstick tube seal, or the pump/torque converter seal at front of transmission.

A high mileage transmission can have a leak at the output shaft due to looseness from bushing wear. This is a fairly simple repair. The output shaft bushing is at the back end of the transmission and the seal will be replaced as part of the service.

Front wheel drive cars can leak fluid around the axle shaft seals, and it can be quite a job to replace these seals.

Will adding transmission fluid stop my transmission from slipping?

Adding transmission fluid to stop slipping will only work if the transmission was low on fluid. Most likely, damage to the internal components has already happened, and repairs will be necessary.

What sensor can cause a transmission to slip?

The transmission range sensor and the speed sensor both can cause erratic transmission shifts and/or gear changes resulting in the transmission not performing correctly. A good transmission shop can check these sensors for you for a small fee,

These sensors are replace-only items as they are not designed to be repaired. Check to see if the wiring harness is plugged into these sensors and is not damaged.

Transmissions can do very crazy things if any of the controlling sensors, their wiring harnesses, or the transmission computer have issues.

A good check of the wiring harness and the plugs are in order when problems are experienced.

Corrosion in the wiring harness plugs has made many technicians have a real problem figuring out what is wrong with the transmission. If you unplug a wiring harness, clean off corrosion and be sure to put dielectric grease in the plug before reassembly. This action will save much grief later, especially in high-humidity areas or where road salt is used in the wintertime.

Sensor signals must be of good quality and not diminished or have static from corrosion.

What does a transmission slip feel like?

Transmission slip will be felt as the engine is revving higher than the vehicle motion would indicate. It is not a good idea to attempt additional movement of the vehicle until the slipping problem is resolved. Much additional damage can occur.

What happens if you put in oil instead of transmission fluid?

Using oil instead of transmission fluid will result in the oil foaming and quite possibly exiting the transmission at its vent. Also the foam will keep the transmission from working properly due to air in the fluid. It will cause damage to the internal components of the transmission.

What happens if you mix power steering fluid and transmission fluid?

Power steering fluid and transmission fluid are similar, but the transmission fluid has additives to prevent foaming, protect seals, and provide the correct friction coefficient for the transmission to work properly. Transmission fluid contains a dye that also helps keep seals from hardening.

Power steering fluid is formulated for the distinct requirements of power steering. It would work in a transmission for a short time, but would not provide the required fluid qualities of transmission fluid.

Can brake fluid be used as hydraulic fluid?

Some hydraulic applications use brake fluid. Check your owner’s manual for the recommended fluid to use.

Never mix brake fluid and hydraulic oil in the same reservoir. They do not play nicely together. Most likely you will have a gummy mess to deal with and all your seals and O-rings will be ruined.

Does transmission additive really work?

Aftermarket transmission additives help the seller’s “bottom line”, but will not help your transmission beyond the short term. Additives could shorten the life of your transmission by lulling you into a false sense of security while continuing damages are progressing.

The best thing to do is keep the seals renewed if they leak, use the proper transmission fluid, and keep it at the correct fill level.

A fluid and filter service should be done at the intervals suggested in your owner’s manual.

Will seafoam help a slipping transmission?

Seafoam or any other additive will only help for the short term. After that, the needed repairs should be made to the transmission.

Automotive engineers have made the best choices they can for the correct seal and O-ring material and combine that with the correct transmission fluid formulation for longevity of your transmission.

Why do I keep losing transmission fluid?

Continuing loss of transmission fluid indicates seal or O-ring failure, or a transmission pan gasket failure.

A good visual inspection after a transmission wipe-down can let you see where the transmission fluid is leaking from.

Place a large flat piece of cardboard under the transmission area of your auto to get a good idea from the fluid drips on the cardboard, just where the fluid is coming from. Use these indicators to look for the fluid drips coming from the transmission. The transmission pan can have a crack in it although not a common problem.