Why does the automatic transmission slip when hot?

The automatic transmission offers a great driving convenience. But that’s not to say it’s perfect as it has its unique set of problems. Notably, transmission slipping after the fluid heats up is a common problem.

Why is my automatic transmission slipping when hot? This may be happening due to a few reasons. These include having a low level of transmission fluid, overused/dirty transmission fluid, worn-out gears, and faulty transmission shift solenoids.

Causes of an Automatic Transmission That Slips When Hot

1. Low Level Of Transmission Fluid

A low level of transmission fluid in your car is one of the major culprits for transmission slipping after the fluid warms up. The problem becomes worse as the fluid heats up more.

Symptoms: apart from your transmission slipping, other symptoms showing that you have a low level of transmission fluid include;

Possible solution: Top up your transmission fluid. You’ll need about 4-12 quarts of fluid to top the decreased fluid levels back up. The fluid costs between $7-$8 to $18-$20 per quart, depending on many factors including the dealer, the model of your car, and the transmission fluid’s brand. That means you can expect to part with $35-$40 up to $300 to have this fix.

2. Overused Transmission Fluid

Overused automatic transmission fluid could be another cause of the slipping issue. This fluid is dirty and it will not do its job efficiently.

Since it won’t be able to generate hydraulic pressure as needed to maintain or switch gears to subsequent levels, the gears will slip, especially when the fluid warms up.

Besides the slipping issue, other symptoms that may indicate that your transmission is overused and needs changing include;

  • An overheating engine.
  • Transmission whining noise.
  • Grinding noises when the engine engages the transmission.
  • Transmission fluid turns from clear or pink-tinted to brown or deep red.
  • An inability for the car to reverse.

Possible solution: Change your transmission fluid. It costs between $300-$500 to have the fluid replaced, depending on the mechanic, the model of your car, and the fluid you choose.

3. Worn-Out Transmission Gears

Transmission gears will wear out over time due to a few reasons. Some of them include the effects of natural wear and tear, not topping up your low transmission fluid, and not changing your overused/dirty transmission fluid.

Worn-out transmission gears will slip especially when the fluid becomes heated. That’s because they’ll lose their ability to engage properly and to slip in as well as out in unison.

Other symptoms to watch out for if you suspect worn-out transmission gears to be the reason behind your gears slipping after the fluid becomes hot include the following;

  • Gears becoming unresponsive.
  • Unusual clunking, banging, or whining sounds coming from the gearbox.

Possible solution: Change your gearbox. It costs between $1800 and $3400 to replace an automatic gearbox. The amount you’ll part with depends on several factors including the mechanic you choose and the model of your car.

4. Faulty Transmission Shift Solenoids

The automatic transmission system has a crucial set of components known as “Shift Solenoid.” Most cars have at least two solenoids.

Located within the valve body of the transmission system, these mechanical devices play a vital role in conjunction with the transmission control module(TCM). Precisely, they regulate the transmission fluid flow.

Bad transmission shift solenoids could be another reason for your transmission slipping immediately after the fluid heats up. To be sure, there are a few other symptoms you can check out, including;

  • The Check Engine light comes on.
  • The transmission warning light comes on.
  • Upshift or downshift problems.
  • Shifting delays.
  • Skipping gears.
  • Sticking gears.
  • Your engine goes into the limp home mode that causes the speed of your car to reduce some features e.g the AC to shut off.

Possible solution: Replace your faulty shift solenoids. It costs about $200 to $500 to have new solenoids installed into your car.

How to Fix a Slipping Transmission?

To fix a slipping transmission, first, determine the cause of the problem. Thereafter, fix it accordingly. For example, if it’s low or overused transmission fluid, top back up or replaces your fluid, respectively.

If it is worn-out transmission gears or bad shift solenoids, replace your gears or solenoids, respectively.

How Much Does It Cost to Fix a Slipping Transmission?

The answer depends on the cause of the problem, which is many, by the way. A low transmission fluid level, an overused transmission fluid, worn-out transmission gears, and bad transmission shift solenoids are just but a few causes. Fixing each cause costs differently as you’ve seen above.

Will a Transmission Flush Fix Slipping?

In some cases, Yes. Transmission flush will correct slipping when the existing transmission fluid is overused and dirty.


Is your automatic transmission slipping when the fluid warms up as you drive? If yes, I hope you now know some of the common causes of that problem and how to fix them.

If it is a low transmission fluid level or an overused transmission fluid, top your fluid back up or change it, respectively. Or if it is worn out transmission gears or faulty shift solenoids, replace your gearbox or solenoids, in that order. Good luck with it.

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