4R70W Fluid Change Procedures

...for the 2001 – 2003.5 Ford F150 (but this may work for other vehicles with the 4R70W)

This writeup provides picture-based instructions for safely and effectively exchanging the transmission fluid in a F150 4R70W transmission with new fluid. There are myriad web pages on the internet for servicing the 4R70W, as it is the automatic transmission commonly used in Mustangs and in Crown Victorias, but very few resources when it comes to servicing the transmission in a truck.

I was personally frustrated with the lack of any useful information on performing the fluid change procedure, so I researched and researched and put together this guide. When I say "useful information", I mean something more than an article written entirely in text and with no explanation of the different parts of a transmission. I believe that anyone with a general knowledge of automotive handywork should be able to do this job on a weekend afternoon.

Before we proceeed, I should explain what exactly is being done in this procedure since I am not simply regurgitating the information in the Haynes manual. The 4R70W in the ’01-’03.5 (Heritage) F150 specifies approximately 14 quarts of Mercon V transmission fluid. Under normal circumstances, approximately 4.5 quarts of MerconV will be present in the actual “fluid pan” of the transmission, with the remaining 9.5 quarts in the torque converter and in the cooler lines. If you are not familiar with the way this transmission is designed in the F150, refer to the diagram below.

(Please excuse the crudeness of my drawing)

Basically, the transmission utilizes a closed-loop cooling system where the transmission fluid is pumped forward of the vehicle to the radiator where it is cooled via the engine fan and airflow when driving down the road. The cooled transmission fluid then returns to the transmission where it is utilized in the valve body and torque converter to keep the vehicle moving forward.

The Haynes manual suggests that you drop the transmission pan to replace the fluid, filter, and clean the magnet. While this does allow you to replace the filter and clean the magnet, you do very little in terms of changing out the fluid since most of it resides in areas of the transmission cooling system that are not accessible. In order to fully exchange the old transmission fluid in the system, you must either empty the torque converter (those of you with ’01 F150s (up until Aug/Sep of 2001) will be able to do this) and purge the cooling lines, or utilize the pump system to capture the old fluid at some point in the closed system.

Since my truck is a 2002, I was not able to access a drain plug in the torque converter. I did some research on some of the more popular forums that discuss the 4R70W (TCCoA, F150online, Stangnet) and found some people mentioning that they were able to use the cooler lines to perform a fluid exchange. I spent about a week contemplating my options and looking around at the transmission and the cooler lines before I committed to purging the fluid via the cooler RETURN line AT the transmission. As you will see below, this turned out to be fairly easy and easily beats dropping the transmission pan (full of fluid) and getting the famous “ATF shower”. You'll also save about $100 that most dealerships charge to hook up a T-Tech machine to perform the flush procedure.


Before you begin…

Prerequisite Knowledge

  • You should have some prior experience on DIY maintenance work. You should be familiar with the terms used in this writeup and understand what is meant when direction is specified on a vehicle (forward, rear, driver-side, passenger-side, etc).
  • Basic tool usage.
  • Know your truck. If your truck has a tow package of auxillary transmission cooler, this will change the fluid quantities I specify below for a stock system.
  • While not required, it would be helpful to know the “cold fill” mark on your transmission dip stick. Some dip sticks (not specifically for the 4R70W in a F150) have a cold-fill mark, but mine did not. This saves some time at the end of the procedure.


  • At a minimum, 14 quarts of Mercon V specification transmission fluid (more fluid = more thorough flush). Note that Mercon V is not a brand, but a lubricant characteristic specification created by Ford Motor Company. What this means is that you do NOT have to get "Motorcraft Mercon V". Frankly, you would be fine using Wal Mart’s Supertech Multi-Vehicle ATF or even Schaeffer’s ATF. As long as the fluid meets or exceeds Mercon V, you will be fine.
  • Quart-measured bucket, at least 5 quarts in capacity. I found mine at Lowe’s in the aisle with buckets and containers. I believe these are supposed to be used for mixing paint, but they work just fine.
  • 3/8” internal diameter clear vinyl hose. You can also find this at Lowe’s, near the aisle where PVC pipe is sold. I found a pre-measured package that was only a few bucks and turned out to be a lot more than I needed. You can always use the rest later for other automotive maintenance procedures. The brand and model for mine was: WATTS SVIG10 42143610 Clear Vinyl Tubing 1/2 in x 3/8 in x 10 ft
  • Clothespin or clamp. This will keep the vinyl hose pointing into the bucket.
  • Large 5-gallon bucket or multiple smaller containers for holding the old transmission fluid. Match the size of this bucket or containers with the number of new quarts of Mercon V that you plan on using.
  • 5/8” Box-End Wrench (the longer the handle, the better)
  • ¾” Box-End Wrench (the longer the handle, the better)
  • 10MM socket and socket wrench(for the transmission pan bolts)
  • Inch-Lb Torque Wrench (where 120-130 in-lb rests in the middle of the torque range)
  • Flashlight and/or work light
  • Safety Glasses
  • Narrow funnel (to be used for re-filling the transmission fluid)
  • Brake cleaner/Carb Cleaner (to clean out the transmission pan)
  • Paper Towels
  • Nitrile Gloves
  • (Optional) Replacement 4R70W transmission filter. (Part No. F6AZ-7A098-A)
  • (Optional) Creeper for easily getting under the truck.
  • (Optional) Junk cardboard for catching any fluid drips.


Time/Other Considerations

  • Expect to spend around 2-3 hours on this procedure. If you can get a helper person, you can probably finish in 2 hours. Always expect the first time to take longer. Follow up procedures should go a lot quicker.
  • Allow the vehicle to cool FULLY before beginning the procedure. You do NOT want to burn your hands against a hot transmission pan or against the heat shields.


  1. Park the vehicle in a cool, level location. Set out all of your materials beforehand so you don’t have to waste time running around.

    (16 quarts of Mercon V lined up for use. I got this during a special at Pep Boys so I only paid $40 for all 16 quarts)

  2. When the vehicle has fully cooled, put on your safety glasses and slide under the vehicle on the passenger side, approximately where the transmission will be.
  3. Position your head/eyes to the space between the transmission and the catalytic converter. You are looking for 2 aluminum/steel hard lines that are bent 90* and enter the transmission via some screw fittings.

  4. The UPPER fitting/line is the RETURN line. This is the line where fluid will come out after it has been cooled in the radiator. You need to loosen the 5/8” nut to make the line open where you can slip the vinyl hose over it. Use the ¾” box-end wrench to keep the ¾” nut in place while you use the 5/8” wrench on the smaller nut to loosen it. I highly recommend you do it this way because I originally just used the 5/8” wrench and was actually unscrewing the larger ¾” fitting from the transmission. Not good, but no harm done. The smaller nut requires very little to be loosened and will spin freely when completely loosened.

  5. Slide the smaller 5/8” nut back and expose the end of the cooler line.
  6. Position your hands so that you can slip one end of the 5/8” I.D. hose over the end of the cooler line as far as possible. Route the tubing around so it does not kink anywhere. Allow the excess tubing to hang down to the ground and cut the tubing where it meets the ground. This will allow you to have enough to route the other half of the tube into the marked quart bucket.

  7. Use the clothespin or clamp to direct the tubing into the bucket. Position the bucket so that you can easily see the quart markings (point the markings toward the driver side if you are working solo). Optional – place the junk cardboard under the bucket so that you do not get any spills onto your garage floor.
  8. Get into the cab of the truck and start the vehicle. Immediately, look below the truck at the bucket and wait for the transmission fluid to begin flowing. You may wait 10-20 seconds for the fluid to fully travel through the lines and exit out. The transmission fluid will fill the bucket quickly, so keep an active eye on when you begin seeing bubbles in the vinyl line, as this indicates that the bulk of the transmission fluid has been sucked out of the transmission pan. On my vehicle, almost exactly 4 quarts was extracted before I started to notice air bubbles in the vinyl line. When you see the bubbles (and you may even hear a difference), immediately turn the truck off. You have now emptied the bulk of the transmission fluid in the pan.

    (Almost exactly 4 quarts extracted from the cooler return line before I started to notice air bubbles in the hose)

  9. Empty the old fluid into your 5-gallon bucket and set the bucket aside. Get under the truck and leave the vinyl hose connected, but move it out of the way. I found a small spot in the frame cross-member where I was able to tuck the hose away.
  10. Use the 10mm socket end to loosen all of the transmission pan bolts. When you begin removing the last few bolts, the pan may want to start dropping, so keep it supported. The pan itself has some weight, but will be considerably lighter since it does not contain an entire 4.5-5 quarts of Mercon V.
  11. Loosen the remaining bolts and slowly lower down the transmission pan. It will still contain some fluid, so be careful and set the pan aside. The filter may or may not drop along with the pan. You need to take it out either way.
  12. Drain the rest of the old fluid inside the pan into the 5-gallon bucket. I think I had around .5-.75 quarts of fluid left in the filter and in the pan.

    (Fluid that remained in the pan after the initial extraction along with old filter and sludged up magnet)

  13. Remove the magnet from the pan and clean it with a towel. Set the magnet aside.

  14. Drain the old fluid in the old filter into the 5-gallon bucket and toss the filter aside.
  15. Use carb cleaner or brake cleaner to clean the inside of the transmission pan.
  16. Use a paper towel to clean up the reusable transmission pan gasket.
  17. Place the clean magnet inside the clean transmission pan, set the reusable gasket onto the clean gasket surface. The holes in the gasket will line up with the pan only one way. While you have the chance, clean all the bolts that hold the transmission pan up. Use a degreaser to clean the threads.

  18. Go under the truck and install the new transmission filter. The internal neck of the filter will slide into the opening on the underside of the transmission.

    If you find it difficult to install the new filter, it's possible that the old orange o-ring is still inside the transmission body. The picture below shows the culprit o-ring that can sometimes separate from the old filter. (Thanks Henry)

  19. Install the newly cleaned transmission pan, and use a cross-bolt pattern to torque all the bolts to 120-132 inch-lbs.
  20. Retrieve the vinyl hose that you tucked away and point it into the measured bucket using the clothespin or clamp.
  21. Fill the transmission with 4 or 5 quarts of NEW Mercon V.

    (You will need to use a long, narrow funnel to fill the transmission fluid from the dipstick tube)

  22. Turn on the vehicle and watch as old Mercon V quickly fills the bucket. Wait until 1-2 quarts is filled and then turn off the truck.
  23. Refill the transmission with NEW Mercon V in the same amount that you just extracted.
  24. Empty the measured bucket, if required.

    (This is the total amount of fluid that was extracted from the transmission -- almost enough to fill a 5 gallon bucket!)

  25. Repeat steps 22-24 until you have gone through 13 quarts of Mercon V.
  26. Sometime during the exchange process, you can shift the vehicle out of Park and into a different gear to flush out old fluid in the valve body. Keep the brake pressed when you are in a different gear and only stay in gear for about 5 seconds. This part is where having a partner is helpful because someone can watch the fluid filling the bucket. I would try not to extract more than 3 quarts at a time.
  27. Disconnect the vinyl hose, and re-connect the cooler line into the ¾” nut. Use moderate torque on the 5/8” nut as it does not require a whole lot to lock again. The truck may have warmed up at this point, so you can break until it cools as the exhaust will have gotten fairly hot from the constant start ups.
  28. Clean up all tools and items under the truck and set them aside. Start the truck and let it idle in park for a few minutes. This will allow the new fluid to cycle through the system. Watch for leaks. If there are no leaks, wipe up any transmission fluid that has leaked to the ground.
  29. Get in the truck and shift into gear and move it back (or forward) to test if Reverse, Drive, Neutral, 1, and 2 work. Take it easy and slowly work the truck back and forward. On some gears, you may experience a slight delay in movement while fluid fills the valve body.
  30. Get out, check for leaks. By this time, the engine and transmission should be warmed up, so check the transmission fluid dip stick to see if you are in the hash marks. Add some fluid if needed, but only a little at a time.
  31. When the truck is moving in all gears, there are no leaks, and you are set on the fluid level, drive the vehicle around the block to test everything.
  32. In the next few days, monitor the transmission fluid level as it will settle and may drop in level as fluid routes its way into all the transmission areas.

Questions? Comments? Concerns? Feel free to contact me at wchong4 [at] gmail [dot] com.