Automatic Transmission Fluid Flush with Pennzoil Platinum High Mileage ATF JWS-3309

Looking back at this process I probably should not have done the tranny fluid flush because at this time (a day after it’s been done) the car seems to have a subtle noise/drone coming out of either the engine or transmission which wasn’t there before. Hopefully I didn’t fuck it up by doing the trans fluid flush.

The process is the same as Power Steering fluid flush. You drain old fluid. Add new fluid to mix with the remaining old fluid. Drain the mix, and continue until the mix is clean and pink.

The NC Miata requires a special type of fluid called JWS-3309 which is available only from a few places. Mazda dealer is the obvious choice. But a cheaper alternative is Mobil 3309 or Aisin JWS-3309 which are both non-synthetic. A new synthetic option is Pennzoil Platinum High Mileage ATF JWS-3309 which is what I got. Genuine Toyota T-IV fluid is also identical and apparently cheap, but I wanted to go with Pennzoil.

The bottom of the tranny pan has a drain plug and a “check” plug, the fill plug is on the driver’s side at the very top of the tranny pan.

The instructions were to drain the fluid. Start the car, put it thru gears for less than a minute while the brake is on, keeping the gear for no longer than 2 seconds or so. Then drain again. RE-fill with 4 QT’s at a time, start the car to run it and repeat the drain process. After the second fill it’s recommended to go for a couple of mile drive, then drain the fluid again and fill it in for the last time.

Unfortunately filling in 4 QT cold wasn’t happening, after 1.6 QT the fluid was pouring out of the check opening. So the solution was to start the car so the dripping stopped and keep filling until it dripped again. Then put it thru gears and keep filling until it drips. Keeping in mind that Park and Neutral positions result in fluid leaking out. So Reverse or Drive were the key to keep the fluid sucking into the transmission to get the correct level in.

This process was thoroughly a pain in the ass and I’m not entirely sure we got it 100% correct. Although I’m leaning towards believing that because the amount we put in was exactly the amount that came out while draining. But the car sounds different… who knows if there’s a break-in period.

Some pix :

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The Pennzoil ATF JWS-3309 is available from Pep Boys at $5.79+ tax which isn’t cheap, and as was recommended 12 QT to flush it, it’s pretty pricey… but cheaper than having the dealer doing for a few hundred bux with possible similar results.