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4th Gen Toyota 4Runner Transmission Fluid Service

My 2003 Toyota 4Runner is a V6 SR5 4×4 that has a non-sealed transmission unit. This system has a transmission fluid dipstick, unlike the later years’ 4Runners that have a sealed transmission with no dipstick. The following procedure outlines a flush and fill of the transmission fluid for my car:

First, remove the 14mm drain plug and let all the transmission fluid from the pan drain out. After everything had drained out, I replaced and tightened the drain plug.

4runner 4th gen draining transmission fluid

I could find very little information online about the gasket that is needed for the transmission fluid plug. So I chose to go into my local Toyota Dealership’s Parts Department to ask for the gasket, which they were very willing to help with. I also picked up the OEM Toyota transmission fluid as well.

You can use any sort of drain pan to catch all of the fluid that comes out (about 4-5 quarts.) This kind of drain pan works nicely:

drain pan

Purchase on Amazon.com: Capri Tools CP21023 Portable Oil Drain Pan, Anti-Freeze, Green

For the sealed transmission of later years, the recommended fluid would be the Toyota WS Fluid. However, with non-sealed transmissions like mine, the fluid to use is the ATF T-IV Fluid from Toyota. I purchased a dozen quarts of the fluid as I would be using about 5 quarts to refill the transmission pan, and the remainder on flushing the radiator cooler lines.

Below are links to purchase by the quart or for a dozen quarts (cheaper option):

Purchase on Amazon.com: Genuine Toyota (00279-000T4-01) Automatic Transmission Fluid
Purchase on Amazon.com: Genuine Toyota Lexus ATF Type T-IV Automatic Transmission Fluid OEM 12 quart Type-4 ATF

4runner 4th gen transmission fluid atf type t-iv

In addition to draining the transmission fluid from the drain plug, I also flushed the transmission fluid that runs through the oil cooler lines to the radiator. There is an inlet oil cooler line and an outlet oil cooler line, both running between the transmission and the radiator. I removed the outlet cooler line on the radiator side, and used a 3/8″ clear hose to attach to the metal piping. The other end of the clear hose was run to the drain pan. This post helped me out a ton with identifying the proper line to use.

4runner 4th transmission fluid flush and fill

I turned on the car for about 10 seconds (not allowing the car to warm up) so that additional transmission fluid would leave the radiator and exit through the oil cooler outlet hose. I then refilled another 2-3 quarts and re-did this several times to “flush” out the fluid. When I was finished, I removed the clear plastic hose, connected the oil cooler outlet hose back to its place, and then prepared to refill the transmission fluid to its permanent level.

To refill the transmission fluid through the dipstick, I use a funnel that specifically fits. Normal funnels don’t fit properly as it needs to be narrow enough for the lower-mounted transmission fluid dipstick location.

Purchase on Amazon.com: Plews 75-068 Super Funnel – 2 Quart Capacity

4runner 4th gen draining transmission fluid

Finally, refill the transmission with 4-5 quarts of transmission fluid. Turn on the car and let it run until it is warmed up. Then then fill slowly meanwhile checking the dipstick level to get it to the proper level. Then you’re all done!

4runner 4th gen transmission fluid dipstick

These two links outline both non-sealed and sealed transmissions and are of utmost value when performing this transmission service on your vehicle:




Hi there! I'm Scott and I run The Track Ahead. My goal is to provide helpful articles and tutorials based on my experience and research related to car maintenance and automotive detailing. When I'm not writing and not working my day job, you can find me spending time with my family and working on home and car projects.


  1. Thanks a lot for your dedication about sharing your experience. So at the end, how many quarts are needed to flush completely the tranny’s fluid? I have been done a rebuild of the same transmission and I have 2 gallons of type IV Toyota fluid. I hope could be enough. Have a great one! And thanks again. Antony.

    • Thanks for the comment! Nice job on the rebuild! With a full rebuild of the tranny, it appears 2 gallons is not enough for the amount of fluid you need.

      If you look at the first link at the end of the post, the member on the T4R.org forum mentions that they have been told by repair facilities that for a full flush and fill on a non-sealed transmission, it would require 18 quarts. I’d do a bit of cross-checking to make sure this number this is correct. Good luck!

  2. Johnny Danger Reply

    Signed up just to make this comment, and your 4runner may be plumbed differently, but your photo of the return line was definitely the FEED line on mine. I got a pretty good hose down from the disconnected hose of some rancid old ATF. For anyone reading this, the return line is the LOWER metal pipe with the less sharp of a bend.

    • Thanks for bringing this up. I can’t recall why it may be different looking, but I do think my post is a bit unclear. Do you have any photos? Can you send to my email at [email protected]? I’d like to look into this in case I got it wrong on my photo.

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