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Ford F-150: Why is My Transmission Overheating?

Too much heat will degrade your transmission fluid and weaken it's internal components. Overheating your transmission regularly will quickly turn your F-150 into a loud, immobile hunk of metal. Figure out why it's overheating with our guide below.

By Pizzaman711 - October 20, 2014

Transmissions have a pretty high tolerance for abuse, but only if their cooling systems are working correctly. Wisely, Ford has kept the transmission cooling system in these trucks pretty simple. Fluid is pumped out of the transmission to the front of the truck where it enters a transmission cooler. Most trucks have an external cooler, but some only use the "in-tank" cooler that's a part of the radiator. So if your truck is overheating, there are only a few problems you could be dealing with: low or high fluid levels, transmission fluid leaks, or clogged lines.

Pro Tip

You can check the transmission fluid temperature on a 2008-present F-150 through the dashboard computer. The maximum temperature for these trucks is around 220ºF. Your transmission will trigger a system warning (either a check engine light, or a flashing overdrive light or a "trans fault" message) if it starts overheating.

Step 1 – Check fluid level

The most likely cause of an overheating transmission is the fluid being too low. To check the fluid the truck will need to be warmed up and running. Drive your truck until the engine is warm and then another one or two miles to make sure the transmission is up to temp.

If the fluid is low, top it off. Too much fluid will churn inside the transmission and foam up resulting in diminished cooling ability. Drain and check until the fluid is at the right level.

  • F-150 transmission fluid dipstick diagram (warm)
    Figure 4. Your transmission fluid should be in this range when warm (approx 150°F to 170°F)
  • F-150 Transmission Fluid Dipstick Diagram
    Figure 5. Your transmission fluid should be in this range when cold.

Take the time to inspect the fluid condition as well. If it’s brown or has a burnt smell, you should change your fluid or it can cause other problems. If it’s pink or foamy, you need to rebuild the transmission in addition to finding your cooling issue.

Note, depending on how long the transmission has been overheating for, your fluid may already be brown and have a burnt smell.

(Related Article: How to Check Your Transmission Fluid - Ford-Trucks.com)

Step 2 – Inspect transmission cooler lines

This is a pretty straightforward step. Just follow the lines from the transmission to the transmission cooler and look for leaks or any breaks. Transmission fluid is red when new, so if you find red-colored fluid leaking around transmission line connections, this is most likely your problem.

  • Ford 4R7xx Transmission Cooler Lines
    Figure 2. Ford 4R7xx Transmission Cooler Lines
  • Ford 6R80 Transmission Cooler Lines
    Figure 3. Ford 6R80 Transmission Cooler Lines

Leaky Transmission Cooler Line
Figure 4. Transmission cooler line with leak circled in red

Step 3 – Inspect transmission cooler

Look for any broken fins or large dents. These could mean interior fluid passages are closed, not allowing fluid to flow. You will need to replace the cooler if it’s damaged.

You should also check your transmission cooler and coolant lines for clogs. Simply follow the lines from your transmission to the front of your truck to find the cooler. If the cooler is cool to the touch, you have a clog somewhere. I suggest wrapping a dishrag around your hand to protect it in case there is no clog.

If you find a clog you can repeat this process on the transmission lines to locate where the clog is.

(Related Discussion: How to Find the Transmission Cooler - F-150online.com )

Step 4 – Backflush transmission cooler and lines

Pro Tip

I recommend taking your truck to a mechanic to have this performed, it’s a very tedious task and one mistake can cost you a new transmission. Note, this is usually recommended as a last resort due to the possibility of it dislodging any loose material that could have been covering pin holes anywhere in the system thus leading to leaks.

If you wish to try this yourself, you will need:

  • Transmission flushing kit (includes hoses and valves to attach to your transmission lines)
  • Transmission cleaning fluid (some people use water from the hose, but this is not recommended)
  • A way to maintain constant fluid flow through the transmission lines
  • New transmission fluid
  • Air compressor
  • Socket/wrench set

For a brief overview you’ll need to:

  1. Drain all fluid from the transmission
  2. Install the flushing kit
  3. Pump the cleaning fluid through the truck while it’s running for 5-10 minutes
  4. Once the fluid coming out is clear you’ll need to shut off the truck and let all cleaning fluid drain out
  5. Using the compressor, blow out all the transmission lines to remove any remaining trash
  6. Refill with the proper amount and proper type of transmission fluid and then check for any leaks

Featured Video: Why is My Transmission Overheating?

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