🔧 Avalon - Transmission Fluid Drain and Refill

Your Avalon uses a sealed Toyota U660-series automatic transmission without a dipstick. This procedure replaces the fluid in the transmission pan, then sets the final level at a specific fluid temperature; it is safer than a pressurized flush on a high-mileage transmission.

Difficulty Level: Intermediate | Estimated Time: 1.5-2.5 hours

Assumption: This procedure is for a routine drain-and-refill with Toyota Genuine ATF WS-equivalent fluid.

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⚠️ Safety & Precautions

• ⚠️ Keep your Avalon perfectly level on four jack stands. An uneven vehicle produces an incorrect fluid level.
• ⚠️ Never work beneath a vehicle supported only by a floor jack.
• ⚠️ Transmission fluid and exhaust components become hot during the final level check. Wear gloves and safety glasses.
• ⚠️ Do not use Dexron, universal ATF, CVT fluid, or additives. Use only fluid explicitly approved for Toyota ATF WS.
• ⚠️ Remove the fill plug before draining. If the fill plug cannot be removed, stop so the transmission is not left empty.
• ⚠️ Do not start the engine after draining until replacement fluid has been added.
• ⚠️ Do not perform a pressurized transmission flush as part of this service.
• Battery disconnection is not required.

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🔧 Required Tools

You'll need the following tools for this repair:

• Floor jack rated 2-ton minimum
• Four jack stands rated 2-ton minimum
• Wheel chocks
• Metric socket set, 10mm-14mm
• 3/8-inch drive ratchet
• 6mm hex-bit socket
• 10mm hex-bit socket
• Torque wrench, 2-20 Nm range
• Torque wrench, 20-80 Nm range
• OBD-II scan tool with Toyota transmission-data capability (specialty)
• ATF fluid-transfer pump with fill hose (specialty)
• Graduated drain pan, 8-quart minimum
• Digital measuring container, 5-quart minimum
• Infrared thermometer
• Mechanic’s creeper
• Nitrile mechanic’s gloves
• Safety glasses
• Shop towels

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Toyota ATF WS automatic transmission fluid - Qty: 5 quarts
• Transmission fill-plug sealing washer - Qty: 1
• Transmission drain-plug sealing washer - Qty: 1
• Transmission overflow-plug seal - Qty: 1

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📋 Before You Begin

• Park your Avalon on a hard, level surface and apply the parking brake.
• Place wheel chocks securely against the tires before lifting.
• Drive only long enough to make the fluid mildly warm. Do not begin with an extremely hot transmission.
• Use the floor jack and four jack stands to raise and support the vehicle at equal height. Verify level front-to-rear and side-to-side.
• Connect the OBD-II scan tool. A scan tool is a diagnostic reader that displays the transmission’s internal fluid-temperature sensor.
• Select the Toyota powertrain data list and locate Automatic Transmission Fluid Temperature or A/T Oil Temperature.
• Confirm the fluid is below 35°C (95°F) before beginning the final level-setting procedure.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Raise and level the vehicle

• Use the floor jack at the specified center lifting points, then support your Avalon on four jack stands.
• Use the infrared thermometer or a level reference to verify the vehicle is sitting evenly.
• Push firmly at one corner to confirm the vehicle is stable before going underneath.
• Level support is essential for accurate filling.

Step 2: Remove the lower engine cover

• Wear safety glasses before working underneath the vehicle.
• Use the appropriate 10mm socket or trim fasteners from the metric socket set to remove the lower cover obstructing transmission access.
• Place the fasteners in order so each one returns to its original location.

Step 3: Loosen the transmission fill plug first

• Locate the transmission fill plug on the side of the transmission case.
• Place the drain pan underneath in case a small amount of fluid escapes.
• Use the 10mm hex-bit socket and 3/8-inch ratchet to loosen and remove the fill plug.
• Inspect the plug threads. If the plug cannot be removed cleanly, stop and do not drain the transmission.
• Always prove you can refill before draining.

Step 4: Drain the old transmission fluid

• Position the graduated drain pan directly beneath the transmission drain assembly.
• Use the 10mm hex-bit socket and ratchet to remove the main drain plug.
• Allow the fluid to drain until the stream slows to drops.
• Use the 6mm hex-bit socket to remove the inner overflow plug if it did not come out with the drain assembly.
• The overflow tube is the internal standpipe that establishes the correct fluid height.
• Measure the exact amount removed with the digital measuring container and note the amount.
• Inspect the drained fluid for burnt odor, metallic particles, or coolant contamination. Fine gray paste is less concerning than visible metal fragments.

Step 5: Reinstall the overflow and drain plugs

• Use shop towels to clean the plugs and sealing surfaces without pushing dirt into the openings.
• Install a new overflow-plug seal and start the overflow plug by hand.
• Use the 6mm hex-bit socket and low-range torque wrench to torque the overflow plug to 1.8 Nm (16 in-lbs).
• Install a new sealing washer on the main drain plug and start the plug by hand.
• Use the 10mm hex-bit socket and high-range torque wrench to torque the drain plug to 49 Nm (36 ft-lbs).
• Do not overtighten the small overflow plug; its torque is measured in inch-pounds.

Step 6: Add the initial fluid quantity

• Keep the engine switched off.
• Use the ATF fluid-transfer pump and fill hose to add Toyota ATF WS through the side fill opening.
• Add approximately the amount measured during draining, then add about 0.3-0.5 quart extra for the final overflow check.
• A normal drain-and-refill is commonly around 3-4 quarts, but the measured amount and final overflow check determine the correct level.
• Do not install the fill plug yet.

Step 7: Circulate the new fluid

• Confirm the drain and overflow plugs are installed and no tools are near moving components.
• Start the engine and keep your foot firmly on the brake pedal.
• Move the selector slowly through P-R-N-D-S, pausing approximately three seconds in each position.
• Move the selector back to Park and leave the engine idling.
• Use the OBD-II scan tool to monitor A/T Oil Temperature.
• Inspect underneath your Avalon for active leaks using the safety glasses and infrared thermometer. Never touch hot exhaust parts.

Step 8: Set the transmission fluid level

• Keep your Avalon level, the engine idling, and the selector in Park.
• When the scan tool shows 35-45°C (95-113°F), position the drain pan beneath the overflow plug.
• Use the 6mm hex-bit socket and ratchet to carefully remove the overflow plug.
• If fluid produces a steady stream, let it drain until it becomes a thin trickle.
• If no fluid exits, use the ATF fluid-transfer pump to add Toyota ATF WS through the fill opening until fluid begins flowing from the overflow opening.
• Allow the flow to become a thin trickle or rapid drip.
• Complete the check before fluid temperature exceeds 45°C (113°F). If it becomes too hot, reinstall the plugs, switch off the engine, and let the transmission cool before repeating.
• A thin trickle indicates the correct level.

Step 9: Tighten the plugs

• With the engine still idling and the fluid at the specified temperature, start the overflow plug by hand.
• Use the 6mm hex-bit socket and low-range torque wrench to torque the overflow plug to 1.8 Nm (16 in-lbs).
• Switch off the engine.
• Install a new sealing washer on the fill plug and start it by hand.
• Use the 10mm hex-bit socket and high-range torque wrench to torque the fill plug to 49 Nm (36 ft-lbs).
• Use shop towels to clean spilled fluid from the transmission case.

Step 10: Reinstall the lower cover

• Use the appropriate 10mm socket or original trim fasteners to reinstall the lower engine cover.
• Tighten small cover fasteners only until secure. Do not crush the plastic cover.
• Use the floor jack to lift your Avalon slightly, remove the four jack stands, and lower it carefully.
• Remove the wheel chocks only after the vehicle is fully on the ground.

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✅ After Repair

• Start the engine and confirm there are no warning lights or unusual transmission noises.
• With the brake applied, shift through every selector position and verify normal engagement.
• Take a gentle 10-15 minute road test. Avoid hard acceleration during the initial test.
• Check for smooth shifts, delayed engagement, slipping, or harsh operation.
• Park on a clean, level surface and inspect beneath the transmission for leaks.
• Recheck the drain and fill areas after the vehicle cools. Do not tighten plugs beyond their specified torque.
• If the old fluid contained metal fragments, smelled severely burnt, or the transmission already slips, obtain professional diagnosis rather than repeatedly changing fluid.
• Take used ATF to an automotive-fluid recycling facility. Never pour it onto the ground or into a drain.

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💰 DIY vs Shop Cost

Shop Cost: $220-$400 (parts + labor)

DIY Cost: $55-$100 (parts only)

You Save: $165-$300 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.0-1.5 hours.

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🎯 Ready to get started?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.

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