A drain-and-fill on the A750F pulls about 4 quarts of Toyota WS ATF; a full system flush takes 11–12 quarts because the torque converter holds half the fluid you can't drain in one pass.
The 4th-gen (2003–2009) and 5th-gen (2010–2024) 4Runner V6 share the A750F 5-speed automatic, an Aisin-built sealed transmission with no dipstick. Toyota markets it as "lifetime" fluid, which is marketing — the fluid darkens and shears down between 60k and 90k miles, and 4Runners that see trailer towing, sustained Phoenix heat, or low-range crawling on washboard show ATF degradation well before that. A 60k-mile drain-and-fill is realistic preventive maintenance. A full flush (3 drain-and-fills with drives in between) at 90k–100k miles is appropriate if the fluid has never been changed.
Fluid choice is non-negotiable: Toyota Genuine ATF WS (P/N 00289-ATFWS) or a verified equivalent (Idemitsu TLS-LV, Aisin AFW+). Toyota's own service manual warns that wrong-spec fluid will harm shift quality and damage the valve body. The cheaper "universal" Dexron/Mercon blends are not interchangeable here — they will shift harshly and shorten the transmission's life. Budget 12 quarts of WS to do a full flush.
A drain-and-fill removes about 4 quarts, leaving roughly 7–8 quarts of old fluid in the torque converter, valve body, and cooler lines. To dilute old fluid effectively, do three drain-and-fills with 100-mile drives in between. After the third, you've cycled the new fluid through every chamber and the system reads about 90% fresh. Skipping the multi-pass cycle leaves you with 60–70% fresh fluid — better than nothing, but not a true service.
The level-check procedure is the trickiest part. There is no dipstick. Fluid level is verified by draining the overflow tube while the transmission is at exactly 104–113°F (40–45°C). Too cold and you'll overfill; too hot and you'll underfill. Use an OBD-II scanner that reads transmission temperature (a basic Bluetooth ELM327 + Torque app works) or an infrared thermometer aimed at the pan. Loosen the 5mm hex check plug at temperature and let excess drip until flow reduces to a slow dribble, then torque to 15 ft-lbs.
| Part | Vendor | Est. price |
|---|---|---|
| Toyota Genuine ATF WS (1 qt) | Toyota | ~$12 |
| Aftermarket Toyota WS ATF (Idemitsu, Aisin) | Idemitsu / Aisin | ~$9 |
| Transmission pan gasket (if dropping pan) | Toyota / OEM | ~$35 |
| Transmission filter (if servicing internally) | Toyota / Aisin | ~$75 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.