Transmission Shifts Fine Until It Warms Up | 4 Causes with Solutions

It is common for the transmission to shift fine until it warms up, but that is not the case for every transmission.

In some cases, this problem can be attributed to leaks, low fluid levels, or worn-out parts. These are some of the possible causes.

As a short explanation of the reasons behind this problem and how to solve it, I am going to give you a few tips.

Check out the following articles to read more about transmission issues:

What Do You Mean by Transmission?

Transmission controls the speed and torque of an engine and helps the driver to drive smoothly.

It is a gearbox that links the engine and the driveshaft.

Currently, most vehicles are equipped with automatic transmissions, but there is another type known as a manual transmission.

There is a major difference between manual and automatic transmission: manual transmission requires the driver to change gears manually, while automatic transmission automatically changes gears using hydraulic pressure.

Transmission Shifts Fine Until It Warms Up

The transmission shifts fine until it warms up because of 04 reasons: low transmission fluid level, transmission fluid leakage, worn transmission parts and dirty transmission fluid.

01. Low Transmission Fluid Level

Low Transmission Fluid Level

Low fluid levels are one of the primary causes of transmission slippage when it is warm.

Low fluid doesn’t lubricate the transmission properly and causes slipping problems.

You can only damage the other parts if you take the necessary steps after the problem arises and continue to drive.

How to Fix

Check the fluid level in the following way

  1. Open the hood
  2. Find the dipstick and pull it out
  3. Clean it
  4. Put the dipstick again in the fluid
  5. Now check the fluid level on the dipstick
  6. Usually, the level should be above the “full” line
  7. If the fluid level is below what it should be, add more fluid to maintain the level.

You can follow the owner’s manual for choosing the appropriate fluid or consult a mechanic.

02. Leaks in the Transmission

Leaks in the Transmission

If there are any leaks in the transmission, it causes poor shifting.

Leaks are also responsible for low fluid levels.

As part of routine maintenance, you should take the time to check whether the seals, pans, and gaskets are leak-free.

How to Fix

If you find any symptoms, like:

  • Fluid underneath your vehicle
  • Clunking sound
  • Burning smell
  • Delay acceleration etc.

It means there is a leak in your vehicle.

Now, make sure the pan and gasket are in working condition.

Change the gasket or pan if they have any leaks.

It would be the easiest solution.

03. Dirty Transmission Fluid

Dirty Transmission Fluid

With time, the fluid is contaminated with metal particles and debris.

Dirty transmission fluid can decrease the quality of the fluid and affect its performance.

That is why the transmission fails during warm-up.

How to Fix

Check the transmission fluid and change it if it looks incredibly black or dirty.

You must change transmission fluid every 35,000 to 60,000 miles if your vehicle has a manual transmission and every 58,000 to 100,000 miles for an automatic transmission.

04. Wear and Tear

Wear and Tear

It is a common cause of transmission slipping in an old vehicle.

When your transmission is old enough, its parts get worn out.

A worn-out transmission part causes the transmission to fail when it is warm-up.

How to Fix

Replacing the worn-out part is the most effective solution.

There are a few other problems that cause transmission shifting problems indirectly.

The problems are:

  • Wrong solenoids
  • Low pressure
  • Clogged filters
  • Wearing bands
  • Faulty gears etc.

Symptoms of a Bad Transmission System

If the transmission fails, you will notice the following symptoms

  • Unwanted gear shifting
  • Burning smell
  • There is no movement of the vehicle, but the engine is running.
  • Leaking fluid
  • Unusual noise
  • Check the engine light.

Transmission Fluid Maintenance

Maintaining the transmission fluid will solve most of the transmission problems. Overheating, delay, slipping etc are common transmission issues due to transmission oil. Maintenance includes adding fluid, checking fluid level and quality, transmission flushing etc.

How to check transmission fluid?

Open the engine hood and find the transmission dipstick. Open it up and check the level indication lines. If it is touching the full line, transmission fluid is full. If not then you should add transmission fluid. You can inspect the color and viscosity to diagnose the quality of the fluid.

How to add transmission fluid?

First, open the dipstick and open it. Clean the stick and push it all the way in. Now find the fill hole which should be near the transmission. Now unscrew the cap and insert a funnel. Fill the transmission fluid gently and check the levels continuously. Keep pouring until it shows full on the stick. Start the engine until smooths operation and stabilizes the fluid. Add more fluids later if necessary. You should never over or underfill the transmission fluid. Avoid cheap and wrong fluids for your transmission. It can damage your transmission.

How to flush transmission fluid?

Sometimes, flushing the old transmission fluid is necessary. When all the oils become dirty and worn out, you should flush all the transmission fluid and refill it with new fluid. There is a cap screwed under the oil pan of transmission. Take an oil pan or a big pot and place it under the cap. Unscrew it gently and the oil will start dripping out. After you drip out all the oil, add a little bit of new oil to flash out any residuals. After that, screw the cap again and refill the transmission fluid patiently. It is a tough process and you should contact a professional for the job.

When should you flush your transmission?

Usually, you should flush the transmission fluid every 30,000-40,000 miles or 2 years.

If you offroad and drive a lot and there is debris and contamination in your transmission fluid, you should inspect and change it immediately.

Benefits of Transmission Fluid Maintenance

There are a few benefits to changing and maintaining transmission fluids. Which are:

  • Improved driving experience
  • Better efficiency
  • Improved fuel economy
  • Reducing transmission problems
  • Improves transmission life
  • Efficient gear functioning
  • Low repair frequency


What Causes a Transmission Not to Shift When It Warms Up?

Low fluid level, dirty fluid level, or if there is any fault in the shift solenoids, your transmission does not shift when it warms up.

Any of the above problems will prevent transmission fluid from lubricating the transmission.

As a result, your vehicle’s transmission slips.

Why My Transmission Not Shift When Cold?

The cold temperature caused various problems like low pressure, leaking in the transmission seals, and freezing fluids.

That’s why your transmission does not shift when it is cold.

Use synthetic fluids to avoid such problems.

Can Temperature Sensor Affect Transmission?

Yes, the Intake Air Temperature Sensor (IAT) is responsible for affecting transmission performance when it malfunctions.

The transmission may have soft- or hard-shifting problems when the IAT malfunctions.

Do Automatic Transmission Need to Warm Up?

Yes, it would help if you warmed up your vehicle’s automatic transmission to get proper performance and avoid other damages.

Nevertheless, don’t leave it idle for too long.

Final Verdict

To prevent transmission problems for a long time, perform regular maintenance.

Furthermore, if any part of the transmission is slipping, it is wise to replace it.

Taking the vehicle to a repair shop or dealership is a good idea.

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