How to Change Transmission Fluid in 3rd Gen Toyota Tacoma (Sealed Transmission) – Complete DIY Guide

The 3rd generation Toyota Tacoma (2016–present) with the 6-speed automatic transmission (AC60F/AC60E) is marketed as having a “sealed” or “lifetime” transmission that supposedly never needs fluid changes under normal driving conditions. In reality, the fluid degrades, accumulates clutch material, and loses its protective properties long before the truck reaches high mileage — especially if you tow, off-road, drive in hot climates, or simply want the transmission to last beyond 150,000 miles. Toyota does provide a service procedure, but many dealers claim it “can’t be done” because there is no traditional dipstick. This guide covers every detail of performing a proper fluid exchange on the sealed transmission yourself.

Why the “Lifetime Fluid” Claim Is Misleading

Toyota uses the term WS (World Standard) ATF in the AC60 6-speed. While it is a highly durable synthetic fluid, independent testing and transmission shops consistently show significant discoloration, oxidation, and clutch material by 60,000–100,000 miles. Burnt or contaminated fluid leads to harsh shifting, torque converter shudder, valve body sticking, and eventual solenoid or clutch pack failure. Performing regular drain-and-fills (or a full flush with the proper method) dramatically extends transmission life and restores smooth operation.

Tools and Parts You Will Actually Need

• 24 mm socket or wrench (drain plug)

• 5 mm Allen (hex) key (fill/check plug on the side of the transmission)

• Fluid pump (hand pump, electric, or Toyota special service tool SST 09843-18040 equivalent)

• At least 12–14 quarts of genuine Toyota ATF WS (do NOT substitute — non-WS fluids cause shifting problems)

• New crush washers for drain plug (Toyota PN 35178-30010) and fill plug (optional)

• Long clear hose and a funnel for the temperature-check overflow method

• OBD-II scanner that can read transmission fluid temperature (Techstream, Carista, or high-end scan tools such as Launch, Autel, or BlueDriver with enhanced Toyota support)

• Jack and jack stands or ramps

• Drain pan with at least 6-quart capacity

• Nitrile gloves and plenty of rags

Locating the Plugs on the 3rd Gen Tacoma Transmission

The AC60 transmission is mounted fairly high, but everything is reachable from underneath:

• Drain plug: bottom of the transmission pan, 24 mm hex, faces rearward

• Fill/check plug: passenger side of the case, about halfway up, 5 mm Allen, slightly hard to see

• Overflow tube: inside the drain hole — when you remove the drain plug you will see a small standpipe (this is the level tube)

Step-by-Step Drain and Fill Procedure (Cold Method)

1. Park on a level surface, engine off, transmission cold.

2. Remove the 24 mm drain plug and drain approximately 3.8–4.2 quarts (varies slightly by 4×2 vs 4×4).

3. Inspect the drain plug magnet for excessive metal — a light gray paste is normal, chunks are not.

4. Replace the crush washer and reinstall the drain plug (torque 20 ft-lb).

5. Remove the 5 mm Allen fill plug on the side.

6. Pump exactly the same amount of new Toyota ATF WS back in as came out (measure it precisely).

7. Reinstall the fill plug loosely.

This method is simple and safe but only replaces about 35–40 % of the total fluid (total capacity ≈ 11.6 quarts).

Proper Level Check Procedure Using the Overflow Method (Required for Accuracy)

The only correct way Toyota specifies to check level is with the transmission at 104–113 °F (40–45 °C) and fluid allowed to drip out the overflow tube:

1. After the initial drain-and-fill above, start the engine and cycle through all gears (P-R-N-D-4-3-2) holding each for 5–10 seconds.

2. With engine running, remove the 24 mm drain plug again.

3. Let fluid drain until it slows to a drip (this may take several minutes).

4. If nothing comes out, add small amounts (4–8 oz at a time) through the side fill hole until fluid drips steadily.

5. When it reaches a slow drip (roughly 1 drop every few seconds), reinstall the drain plug with a new crush washer (torque 20 ft-lb).

6. Shut off engine, top off through the side plug if needed until full, then torque the 5 mm Allen plug to 30 ft-lb.

How to Perform a Full Flush (12+ Quarts) Without a Flush Machine

Many owners want to replace nearly all the old fluid. The safest DIY method is the “cooler line disconnect” procedure:

1. Complete 3–4 normal drain-and-fills first to get clean fluid in the pan.

2. Locate the upper transmission cooler line at the radiator (driver-side tank).

3. Disconnect the metal line going INTO the radiator (return line) and route it into a large container (5-gallon bucket with measurement marks works great).

4. Have a helper start the engine in Park.

5. Fluid will pump out rapidly — shut off the engine after exactly 3–4 quarts come out.

6. Add the same amount of new WS through the side fill hole.

7. Repeat until you see bright red clean fluid coming out (usually 12–14 quarts total).

8. Reconnect the line, then perform the temperature overflow procedure above to set the final level.

Recommended Service Intervals for 3rd Gen Tacoma

• Normal driving: drain-and-fill every 60,000 miles

• Severe duty (towing, off-road, hot climate, stop-and-go): every 30,000–40,000 miles

• If fluid is already dark or burnt: perform the full 12–14 quart flush immediately, then follow the severe-duty schedule

Common Mistakes That Destroy These Transmissions

• Using universal or Valvoline MaxLife, Amsoil, Red Line non-WS, etc. — causes harsh 2-3 and 4-5 shifts within a few hundred miles

• Overfilling — leads to foaming and overheating

• Setting level when cold or when too hot (>115 °F)

• Skipping the overflow temperature check and just “filling to the hole”

• Reusing old crush washers — they leak and you lose fluid on the trail

Signs Your Transmission Fluid Needs Attention Now

• Harsh engagement into Drive or Reverse

• Flare or slip on the 2-3 or 4-5 upshift

• Shudder under light throttle (torque converter clutch issue)

• Fluid on the bottom of the pan is dark brown or smells burnt

• Check Engine Light with codes P0741, P0776, P2714, P2757 (common solenoid codes caused by dirty fluid)

Following this procedure with genuine Toyota ATF WS will keep your 3rd Gen Tacoma’s 6-speed shifting smoothly for hundreds of thousands of miles — far beyond what the “sealed for life” marketing suggests.