What Causes Transmission Slipping and How to Fix It

Transmission slipping is a common problem in the automotive communities. Transmission failure has a tendency of occurring when you are far away from your tools or a garage.

In my experience, transmission problems can be challenging to diagnose, and in most cases, hard to patch-up for a hobby mechanic.

There are even some professional repair shops that would choose to replace instead of repair. This is so since specialized equipment and expertise is needed to service the transmission internally.

Although, some transmission problems are specific to a particular model, make, or year of a car, some issues can be diagnosed and fixed as long as you have the appropriate transmission slipping fix skills.

What is Transmission Slipping?

Transmission slipping is the sensation that your transmission is not connected to your engine when you press the accelerator. This usually happens in manual transmission cars when the clutch wears out and loses grip intermittently.

Automatic transmissions were supposed to end this problem, but slipping still happens for a number of reasons. This could require a transmission slipping quick fix or could mean you require a new transmission.

A word of advice is to stop driving the vehicle as soon as you feel something is wrong with the transmission. Prolonged driving could lead to excessive damage to an already weakened transmission.

What Causes a Transmission to Slip?

  • Low Fluid Level

If the level of your transmission fluid is too low, the pump draws in air and mixes it with the fluid. Air is compressible, so the aerated fluid takes longer to pressurize the hydraulic circuits.

The reduced as well as fluctuating pressure signals can wreak havoc on your transmission valve body. The valve body is made up of passages and calibrated valves engineered to work at prescribed hydraulic pressures.

Air in the hydraulic system due to low fluid levels may cause a valve to partially apply a clutch, causing the transmission to slip, or the transmission may end up with inadequate pressure to apply anything. The result is neutral to all gears, the car will simply not move.

Not only does aerated fluid create pressure problems, but it will also run hotter. This potentially leads to accelerated fluid oxidation, sludge and varnish buildup.

  • Burn or Worn Out Fluid

Usually, the structure of the fluid breaks down over time, making the fluid darker and thinner. If the fluid is burnt, worn out, or too thin, it will be ineffectual at getting rid of the heat, and it will not be capable of keeping the clutches and bands sufficiently cooled.

As a result, this causes the transmission to overheat, inhibiting it from shifting gears in the ideal manner. A complete overhaul is usually necessary, and the converter, cooler, and cooler lines will need to be flushed.

  • Transmission Fluid Leak

A leak of the transmission fluid can be caused by a number of reasons, including normal wear and tear, accident or impact, and lack of changing the fluid regularly.

A fluid leak results into low fluid levels, which will likely cause slipping transmission. A leak can arise from anywhere, including faulty seals, cracked torque converter, a worn out pan, gasket, and ruptured fluid lines.

Slipping may be the least of your problems if you continue driving your car with an existing leak. You should check it and have it sealed.

  • Clutch Problems

When a clutch fails, at least four conditions are created most of the time, which include slipping, dragging, chattering, and creeping.

A sleeping clutch is apparent when car speed does not keep pace with engine speed. A slipping clutch, which is often mistaken for an engine defect, causes an engine to use more fuel and may result in overheating.

A friction material separates the transmission and the engine and throws out bearings during a gear change. You will not be capable of fully engaging the clutch as well as shift gears.

The torque converter and transmission of automatic vehicles contain clutch plates for engaging the different gears. You will not be able to shift gears smoothly if the plates are worn out, resulting into transmission slipping.

  • Worn Out Gears

Another common cause of slipping transmission is worn out gears. It is normal for gears to suffer normal wear and tear, and sometimes they may malfunction. Frayed or worn gears do not properly link together, thus a replacement is necessary.

  • Solenoid Problems

In most cases, a transmission solenoid can malfunction due to dirty fluid and electrical issues, which can cause the shift solenoid to close or stuck open.

A defective transmission solenoid can cause the gearbox to skip a gear, get stuck, shift from side to side, or even refuse to shift at all.

  • Torque Converter Problems

Many transmission problems, including slipping, are related to the operation of the torque converter. Usually, torque converter problems will cause abnormal noises, poor acceleration in all gears, and transmission overheating.

If your car lacks power during acceleration, it has a restricted exhaust or the torque converter’s one-way stator clutch is slipping and not allowing any torque multiplication to take place in the converter. Normally, a torque converter replacement is necessary.

Transmission Slipping Symptoms

How to tell if your transmission is slipping? There are various symptoms to look for. Most of the symptoms you are already familiar with.

Check Engine Light

The very first sign that you should look for when you suspect you have a slipping transmission is the check engine light. Modern automobiles are fitted with powerful sensors for detecting engine and transmission problems.

The check engine light is a positive thing. It is alerting you to a problem. If you respond to the warning sooner than later, then, in the long run, you can avoid letting the problem get worse and ultimately paying a higher price for a more extensive repair.

Error Codes

If the dashboard of your car displays the check engine light, then there is a high chance that one or more error codes will show up on your code reader or scan tool. The most popular transmission error codes that you should be concerned about are:

  • P0750-P0770

This range of codes indicates that there is a shift solenoid failure. A specific gear will undoubtedly fail to work accurately if the shift solenoid that is supposed to control it malfunctions. Other error codes may also show up on the reader.

  • P0218

If you see this error code, then it means your transmission is suffering from overheating. Overheating is the most common problem when transmission fluid levels are low, malfunction of the cooling fan, or when the lines are restricted.

  • P0729-P0736

All the error codes in this range signal gear ratio problems. This codes will show up if there is a spoiled solenoid, torque converter malfunctions, or when the transmission fluid level is low.

  • P0613

This is an automatic transmission related code. This code has everything to do with the TCM. It can be generated by a shorted TCM or a bad electrical connection.

  • P0706

The info regarding the gear your car is in, is usually conveyed to the PCM and TCM via the transmission range sensor circuit or performance. A defective sensor, dirty fluid, or a corroded manual shift valve linkage can produce this error code.

Check out more error codes related to transmission problems.

Shifting Delay

What happens when a transmission slips? Shift delay or lack of response could happen. Delayed shifts can be caused by transmission slipping or your engine running so badly that the throttle paddle must be pushed to the floor to keep it running or get it going.

If you are driving an automatic vehicle, you will observe a delay when shifting into park or drive before you are able to engage the gear. This should directly tell you the problem is transmission related.

You will also experience a similar lack of response with manual transmissions. However, the RPMs of the engine will surge after shifting successfully into gear. This is normally a clutch problem, and a replacement may be necessary.

Automatic Transmission Slipping When Accelerating

You may experience slipping feeling on first acceleration. You will notice a change in rpm or speed, such as the car hesitates from 0 to 20 kilometer per hour and then the speed normalizes above the 20 marks.

Noises

A noisy vehicle can be quite embarrassing and annoying. Any kind of noise, including whining, howling, growling, and grinding, can mean a big problem.

A high-pitched, steady noise coming from the transmission is basically gear whine. Whining varies in loudness and frequency with speed and the gear selected.

Whining is common with many transmissions, and it is another sound that may not be easy to cure. Some types of gear whine are related to transmission problems, but others are simply the result of specific gear tooth shape, oil, or wear.

Regardless, when gear teeth wear and pitting takes place, whining will start. As the gear teeth continue to worsen, the whining will become a louder howling.

A growling noise can be caused by bearings that are worn and badly damaged. When this is the case, bearing damage has occurred throughout the transmission. So, growling can be an indication that a complete overhaul will be necessary.

Grinding or clashing noises during upshifts and downshifts are fairly common on manual transmissions. In some cases, it could be as simple as you not fully disengaging the clutch between shifts and may be solved by pushing the clutch pedal all the way to the floor.

Vibration

How to tell if the transmission is slipping apart from the noises? In addition to noises, another common sign is vibration. Vibration can be caused by many things, but vibration is coming from the transmission is normally a sign of extreme wear in the bearing and/or the gear teeth.

Transmission vibration is usually followed by whining, growling, or knocking and designates failure to have the car fixed in a timely fashion.

Hard Shifting

During the life of your car, components wear, and hard shifting can occur. Hard shifting is when the shifter does not move smoothly into the appropriate gear and needs excessive force for you to force it into gear.

Hard shifting may also be accompanied by grinding gears. Hard shifting concerns can be the outcome of an incorrectly adjusted clutch or other clutch problems.

You are most likely to experience hard shifts if you are experiencing low fluid levels. As I mentioned earlier, low fluid level alters the transmission’s operating pressures. This significantly reduces lubricants around the bands and clutches, increasing transmission temperature.

Lazy/No Starting

A lazy start is most certainly a transmission slipping problem, particularly in cold weather. If your car fails to start when you push the pedal, means that the transmission fails to latch on time when the gears move, causing slipping.

Lost Reverse

When doing highway driving at fast speed, you are likely to lose reverse. This happens when you shift the automatic transmission into reverse. This symptom is mainly observed in cold weather.

Burning Smell

You may experience a burning smell when your car struggles to speed up with your foot on the accelerator. Your clutch and/or pressure plate may be worn out. When a clutch is slipping, you also get a burning smell, and the car will not accelerate as engineered.

Changing Oil Characteristics

Usually, good quality transmission oil is supposed to smell pleasantly sweet and has a clear to bright-red appearance. However, aging, leaking, or low fluid levels may interfere with the integrity of the oil, causing it to smell awful, become thinner, or change color.

How to Fix a Slipping Transmission

There are a number of ways that you can learn, how to fix a slipping transmission. However, all the transmission slipping fix techniques that you can perform on your own without the help of a specialist are based on simple transmission problems.

How to Fix Slipping Transmission Using Transmission Fluid

You can fix issues related to ineffective or burnt fluid and low fluid levels. This will mostly require you to change the fluid or check the fluid level and physical characteristics.

Low Fluid Levels

To solve slipping due to low fluid levels, you will need a funnel and an appropriate transmission fluid.

Procedure:

  1. Step One: Warm the fluid by starting your car.
  2. Step Two: Open the hood and pull out the transmission measuring stick or dipstick.
  3. Step Three: Ensure the fluid levels fall between the “Full” &”Add” marks on the measuring stick.
  4. Step Four: Add more of the appropriate transmission fluid if the fluid level is low. Use a channel to pour the fluid into the reservoir.
  5. Step Five: Start your car once again and check if the slipping is over.

Burnt Fluid

If the burnt fluid is the cause of slipping, you will need the following: transmission fluid, clean rags, a funnel, wrench, fluid container, transmission filter, and ramps.

Procedure:

  1. Step One: Check the physical state of your fluid to confirm its integrity. You will need an oil change if it is black with a burning smell or if it is dark brown with particles.
  2. Step Two: Use your jack stands to elevate your car, then start the engine to warm it up.
  3. Step Three: Pinpoint the transmission fluid pan. Usually, the pan is bolted to the bottom part of the transmission. Inspect the pan, then drain the fluid by pulling out the drain plug, and allow the fluid to flow into a receptacle.There are some vehicles that may need you to remove the entire transmission pan. You will have to unscrew the pan in order to get it free. You can always free the pan to conduct a thorough inspection of the gaskets, filters among other components.Drain the Fluid and let it collect on the pan to avoid messing the floor. You may need a wider pan if your transmission is not fitted with a drain plug.
  4. Step Four: Inspect the draining fluid and check for metal shavings. Most pans of the automatic transmission are equipped with a magnet to capture any metal shavings. You should be concerned when the metal shavings are odd-shaped or large.
  5. Step Five: Inspect the gaskets and filters to check if they are operational. Normally, leaky or cracked gaskets and filters have to be replaced with similar parts. If you are not sure what to buy, you can simply ask the technicians at the auto store or contact us for free advice.
  6. Step Six: Add new fluid. Once you have reattached the pan, remove the
    jack stand and fill in new transmission fluid. Make sure you use the appropriate fluid as recommended by your car maker. Avoid overfilling.
  7. Step Seven: Start your car and run it for a while. The slipping should stop after fluid replacement.

How to Temporarily Fix a Slipping Transmission Using Stop Leak or Additive

I can suggest the use of stop leak or additive in only a few situations. One is a stop-gap situation. The use of a stop leak should do the trick.

Another situation might be when there is an excessive amount of sludge and varnish in the fluid. Before changing to fresh fluid, you might try an additive with an extra dose of dispersant or cleaner to scrub the transmission innards.

Procedure:

  1. Step One: Check the origin of the leak. You should look for a puncture or a hole in the casing of the transmission, cooling line or cooler leaks, and leaking seals or gaskets.
  2. Step Two: Consider the amount of leakage you are dealing with. You will most likely need a top-tier stop leak to fix the problem if you find just a few drops on the floor.Pull out the dipstick to check the level of the fluid before you add the stop leak. If the level is low, replace lost amount to the right level and add the stop leak.

You should consider using a stop-gap measure to fix major leaks that are causing transmission slipping. If the leak worsens, you will have to see a mechanic for a more effective and permanent fix.

How to Stop Leaks by Replacing Parts

There are some leaks that may need you to replace the affected parts. Here are a few things you can do on your own.

Procedure:

  1. Step One: Locate the source of the problem by examining the seals, fluid lines, gaskets, torque converter, and transmission pan.
  2. Step Two: Establish whether or not the leak can be stopped. You may only need to add a stop leak if there are only a few drops on the ground.
  3. Step Three: Find out what you require. This may include: jack stands, fluid pan, a funnel, transmission fluid, and new hose clamps, cooler lines, gaskets, seals, pan, and drain plug.
  4. Step Four: Follow the procedure for draining the transmission fluid as discussed above.
  5. Step Five: Resolve the problem once you have drained the fluid, which can include: replacing or tightening pan bolts, and replacing the pan, fluid lines, gasket, and seals.
  6. Step Six: Now, go ahead and add fresh transmission fluid (as recommended by your vehicle manufacturer).
  7. Step Seven: Warm up your vehicle and then shift through the various gears to evenly disperse the fluid. This should fix the slipping problem.

Conclusion

The main objective of diagnosing a slipping transmission should be to identify the problem, preferably without removing the transmission. Then you will know which internals to examine more closely on teardown, providing that a rebuild is imminent.

Otherwise, you may waste time jumping from one thing to another without accomplishing anything. Always start by checking the most and easiest to remedy problems, then proceed to the most difficult to find and fix.

For example, it would be pointless to go through exhaustive tests to identify the source of a transmission slip without first checking the fluid level, fluid condition, or leaks. It will also be unwise to assume the worst without a detailed inspection.

You can only come up with an effective transmission slipping fix if you read the symptoms. Because an automatic transmission is a closed system, with fluid travelling throughout, one failure can cause another in a seemingly unrelated area.

Avatar for Jason Hennessey

I have lived and breathed the automotive sector for over 7 years. As a taxi driver, fleet owner, garage services provider, I have gained the knowledge and passion for providing a service that is fair for everyone involved in the ride-hailing industry. I'm always looking for the next big thing in this industry, and I'm always happy to share it with others with product researches, reviews, and useful tips.

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