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  • Jason

Transmission Fluid Exchange

Updated: Apr 3, 2021

The 5th gen 4Runner “sealed” transmission does not have a dipstick, however it is easily servicable with a few common tools. The following tutorial will provide a walkthrough to properly cycle and replace your transmission fluid to ensure a long service life.



Difficulty: Moderate

Frequency: Every 36 months or 30,000 miles (see my thoughts at the end)

Estimated time: A few hours (much easier with a lift)

Estimated cost: Depends on the fluid used, $200


Toyota OEM WS transmission fluid: 00289ATFWS

MSRP: $10.91 (per quart)

Proper fill in entire system (not pan) is 12 quarts


Toyota OEM transmission filter: 3533060050

MSRP: $63.62


Toyota OEM filter o-ring: 9030131014

Toyota OEM fill gasket: 9030115004

Toyota OEM drain gasket: 3517830010

Toyota OEM check gasket: 3517830010

Toyota OEM pan gasket: 3516860010


Tools Required: 24mm socket, 14mm socket, 5mm allen hex, torque wrench, spring clamp removal tool


While true “flushes” are generally regarded as not necessary (or not desirable) this process outlines a ”fluid exchange” process which gradually introduces new transmission fluid into the system without chemicals or high pressure. This is a very slow process but it guarantees proper fluid exchange without damaging internal components. If your rig is over 120k miles without any previous transmission work or fluid change, this process or any transmission fluid swap is not recommended.


1. Lift your truck onto jack stands for clearance and make sure that the truck is level. For Limited models or just for additional working room, remove the front passenger side wheel assembly.



2. Locate the transmission fill bolt towards the top of the transmission. It should have a “WS” logo on it as shown.



3. Using a breaker bar, remove the fill plug with a 24mm wrench. Once you have confirmed that removal is possible, carefully hand tighten the plug back into the transmission so it is snug - not loose and not tight.


NOTICE- If you cannot loosen the fill plug, do not advance any farther! You may damage your rig if you drain your transmission and cannot refill it yourself - it is always best practice to loosen the fill plug first!


4. Locate the transmission fluid return line, coming from the radiator. It is next to the lower radiator line.

5. Remove the spring clamp and remove the hose from the fitting.

6. Attach a temporary tube to the radiator fitting and insert the other end into a container with 2L/2qt markings. This step will minimize spills during the ”flush”.


7. Turn on the vehicle until approximately 2 quarts of fluid is removed into the container, and then turn the vehicle off. Set aside a small sample for reference. Also collect a sample for fluids analysis at this stage, if testing is desired.


Pro Tip: While this is best to do with two people - one person starting the vehicle and the other person watching the fluid level, it is possible to do it alone. If you have an Apple Watch/iPhone, you can use your iPhone as the camera and your Apple Watch as the viewfinder. This was much more effective (and safer) than running back and forth in my small garage.


The fluid should be anywhere from a dark brownish red to a clear cherry red. If your fluid is black, has visible chunks, thick, or has shiny chunks/shavings - STOP. Your transmission is most likely going to have problems if you continue with the full process. Follow the next step and bolt everything back together before taking your rig in for service at your local mechanic or dealer.


8. Remove the hand tight fill bolt and add 2 quarts of new WS fluid into the transmission. I use the hand transfer pumps from Harbor Freight. To minimize spilling, I put the quarts into an empty plastic container.

The fill tube can be placed over the exhaust which will hold it nicely in place - just remember to remove it after every fill cycle and replace with the fill bolt. If you don’t, the fill tube may melt and some fluid may seep out of the fill hole.


9. Repeat this process approximately 3 times. If you are worried about deep cycling your starter battery, connect to a charger between each drain.



Compare your first sample to your fourth - if the result is “closer” to the clean new fluid, then continue with 2 more cycles. If it looks the same, repeat this process 1 more time and check again. If there is no improvement, proceed to step 10 for filter replacement.


The photo on the left is from the first drain. The photo on the right is after 3 cycles.

NOTE: The next step considers that the full (8) cycles were completed successfully, showing improved fluid appearance with each flush closer to the OEM new fluid.


The photo on the left is after 5 cycles. The photo on the right is new fluid for comparison.


10. Remove the temporary tube and reattach the transmission return line to the radiator. If you are reusing the spring clamp, you must position the clamp in the same position as it was originally so there are no leaks. The temporary tube can be reused in the future.


11. Locate the transmission pan on the passenger side of the vehicle. Remove the plastic skid plate extension to give you full access to the pan.

12. Remove the drain bolt, not the check bolt (highlighted below) and measure the fluid removed. The pan should hold approximately 1.8 quarts. Add the new crush washer and retorque the drain bolt to 15 ft-lb.

13. Remove the (20) bolts holding on the pan and remove it. It is a good idea to leave (4) bolts in the corners and place a jackstand underneath to help prevent the pan from falling to the floor. I also mapped out my pan bolts, so that the bolts can be put back in the exact position afterwards.


14. Clean the pan carefully (no cleaning chemicals) and wipe until clean and dry with lint free towels. Inspect the magnets and take photos documenting the metals found. Also clean the outside to prevent the buildup of salt/dirt which will start corrosion. (clean pan shown)

The magnets contained a very fine powder - no chunks or shavings found.

15. Remove the (4) bolts securing the filter to the transmission. The filter should pull straight down out of the housing.

16. Check that the o-ring was also removed with the filter or manually find and remove it from the transmission body.

17. There are (19) bolts in the valve body assembly, retorque to 8 ft-lbs

18. Install the new o-ring on the new filter and attach to the valve body with the four (4) original bolts, torqued to 7 ft-lbs. The filter will “click” into position when inserted.

19. Remove the old gasket from the transmission pan. My gasket was easy to remove and was not dried out. If stuck, use a plastic (non-gouging) tool or a razor blade. Do not gouge or dent the sealing area when removing the old gasket. Do not use steel wool or any scratching/scuffing medium to clean this seal surface. If you follow the recommended service interval above, you will most likely not encounter problems with removing the gasket in the future. You want a clean smooth sealing surface on both the pan and the valve body.


20. Make sure the gasket is aligned to the correct side, there is a slight taper on the one side. Adhere the new pan gasket to the clean pan with a very small amount of silicon. Tape 4-6 bolts into the holes as “guides”, making sure that the tape does not potentially enter the pan/seal area. This is the best way that I have found to hold the gasket in place without twisting or other issues.


21. Reattach the pan to the assembly using the (20) bolts removed previously, torque to 62 in-lb. Start with (2) bolts on each long side and then remove the tape, installing and torquing the rest of the bolts. With your finger nail between the pan and transmission body, feel for the gasket around the entire perimeter of the pan. If you feel the gasket at the same depth and is a consistent face (meaning no twisting), you know that the gasket is installed properly.


22. Fill the transmission with the amount of fluid drained in step 12. If you do not remember or did not check, you can fill with 2.0 quarts of new fluid. Remember to swap out the fill plug gasket before torquing down to 27 ft-lbs.


23. Turn on the vehicle and allow approximately 10 minutes to shift through all the gears and go for a quick 10-15 minute drive. You want the fluid to be between 104F and 113F per Toyota’s recommendation. Some people use infared guns on the pan but that is not as accurate as the actual reading which can be read through the OBDII port.


I use a Scangauge II to monitor this temperature - see my detailed review for all the capabilities and benefits of a Scanguage.


24. With the vehicle on and up to temperature and ensuring the that transmission pan

is level, remove the check bolt.

- If no fluid appears, you are underfilled. Retorque the check bolt, add (1) quart of fluid and repeat steps 23 & 24.

- If a small dribble or slow flow appears, you are properly filled. Retorque the check bolt, and you are done.

- If a stream appears, let the pan drain down to a small dribble or slow flow before retorquing the check bolt.


29. Reinstall the check bolt with a new crush washer, torqued to 15 ft-lb. Repeat the same 10-15 minute drive and then check again for leaks. If there are no leaks, you are good to go.


In my opinion, the actual fluid exchange process is very straight forward and easy enough to do on a driveway/home garage. While the recommendation for exchanging (or not exchanging, if you ask the dealer) is pretty long, I like to think that transmission fluid and one afternoon is cheap here and there versus the cost of a new transmission. I tend to drain/fill/check the transmission fluid at least one cycle every 3rd oil change. By always keeping new fluid circulating and changing the pan filter/gasket on a regular cycle, you are maintaining your AT as much as possible without wasting money.

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