🔧 Flex - Transmission Fluid Drain & Refill

On your Flex, a drain-and-refill replaces a large portion of the old automatic transmission fluid (ATF) without doing a machine “flush.” This helps restore shift quality and heat protection while keeping the job beginner-friendly.

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

Assumption: Your Flex uses the 6-speed 6F50 automatic and MERCON LV ATF.

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⚠️ Safety & Precautions

• ⚠️ Work on a level surface; support the vehicle securely.
• ⚠️ Use jack stands—never rely on a floor jack alone.
• ⚠️ Transmission fluid can be very hot; let it cool enough to avoid burns.
• ⚠️ Keep the vehicle stable when running the engine during the level check.
• ⚠️ No battery disconnect is required for this service.

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🔧 Required Tools

You'll need the following tools for this repair:

• Floor jack (rated 3-ton minimum)
• Jack stands (rated 3-ton minimum)
• Wheel chocks
• Safety glasses
• Nitrile gloves
• Drain pan (at least 10-quart)
• 3/8" drive ratchet
• 3/8" drive torque wrench (10-100 Nm range)
• Socket set (8mm, 10mm, 13mm)
• Flat trim clip tool
• Fluid transfer pump (specialty)
• Long-neck funnel
• OBD2 scan tool with transmission temperature (specialty)
• Infrared thermometer
• Shop rags

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Automatic transmission fluid (MERCON LV) - Qty: 6 quarts
• Transmission drain plug seal - Qty: 1
• Brake cleaner - Qty: 1

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📋 Before You Begin

• Park on level ground, set the parking brake, and place wheel chocks behind the rear wheels.
• Warm up the transmission with a 10–15 minute drive so the old fluid drains more completely.
• Plan to do the final level check with the vehicle sitting level (not nose-up).
• Tip: Cleanliness matters—keep dirt out of the fill point.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Raise and support the front of the vehicle

• Use a floor jack (rated 3-ton minimum) to lift the front at the approved front jacking point.
• Set the vehicle down onto jack stands (rated 3-ton minimum).
• Confirm it’s stable before going underneath.

Step 2: Remove the lower splash shield (if equipped)

• Use an 8mm socket and flat trim clip tool to remove the screws/clips holding the shield.
• Set fasteners aside so you don’t lose them.

Step 3: Drain the old transmission fluid

• Place a drain pan (at least 10-quart) under the transmission pan drain.
• Use a 3/8" drive ratchet to remove the drain plug (many Ford drains accept a 3/8" ratchet directly).
• Let it drain until it slows to an occasional drip.
• Clean the plug and sealing surface with shop rags and brake cleaner.
• Install the new transmission drain plug seal (if separate).
• Reinstall the drain plug and Torque to 35 Nm (26 ft-lbs).

Step 4: Add new fluid (refill)

• Lower the vehicle if needed to keep it level for filling (use the floor jack and jack stands as required).
• Access the transmission fill point:
  • If there’s a top fill/vent: remove the intake duct/airbox fasteners with a 10mm socket to reach the fill/vent opening.
  • If your unit has a side fill plug: use the correct socket set (8mm, 10mm, 13mm) to remove the plug (location varies by build).
• Use a long-neck funnel or fluid transfer pump (specialty) to add MERCON LV.
• Add back roughly the amount you drained (most drain/refills are about 4–5 quarts).
• Tip: Pour slowly to prevent burping and spills.

Step 5: Set the fluid level at temperature

• Start the engine and keep your foot on the brake.
• Move the shifter slowly through all gears (P-R-N-D and back), pausing 2 seconds in each, then leave it in PARK.
• Monitor transmission fluid temperature:
  • Preferred: use an OBD2 scan tool with transmission temperature (specialty).
  • Backup: use an infrared thermometer on the transmission pan (less accurate).
• When the fluid is warm (typical check range is around 80–90°C (176–194°F)), verify level using the transmission’s level/check plug system (varies by build):
  • If there is a check plug: use a 3/8" drive ratchet to remove it with the engine idling.
  • Proper level is a small steady drip or thin stream; if nothing comes out, add fluid in small amounts using the fluid transfer pump (specialty), then recheck.
• Reinstall the check/fill plug and Torque to 12 Nm (9 ft-lbs) (small plugs are low-torque—do not overtighten).

Step 6: Reinstall the splash shield and final cleanup

• Reinstall the shield using an 8mm socket and flat trim clip tool.
• Wipe any spilled ATF and spray remaining residue with brake cleaner.
• Remove tools from under the vehicle, then lower it using the floor jack.

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✅ After Repair

• Test drive 10–15 minutes and confirm smooth shifting.
• Recheck for leaks around the drain plug and any fill/check plug.
• If you notice slipping, harsh shifts, or flare, stop driving and recheck the level (too low or too high can both cause problems).
• Dispose of used ATF responsibly (most parts stores accept it).

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💰 DIY vs Shop Cost

Shop Cost: $250-$450 (parts + labor)

DIY Cost: $45-$90 (parts only)

You Save: $160-$405 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-2.5 hours.

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🎯 Ready to get started?

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