🔧 Optima - Automatic Transmission Fluid Drain/Fill (Level-Set)

Your Optima uses a sealed-style automatic transmission that’s checked by fluid temperature and a level/overflow plug (not a dipstick). The job is a controlled drain, refill, then a final level-set at the correct temperature so the transmission isn’t overfilled or underfilled.

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

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⚠️ Safety & Precautions

• ⚠️ Work on a level surface; support the car with jack stands before going underneath.
• ⚠️ Let the exhaust and transmission cool enough to avoid burns.
• ⚠️ Hybrid caution: keep ignition OFF, key/fob away from the car, and do not touch any orange high-voltage cables/connectors.
• ⚠️ Do not rely on a jack alone; use properly rated jack stands.
• 🔋 Battery disconnect is not required for a basic drain/fill, but keep the vehicle OFF until instructed.

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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, pair)
• Wheel chocks
• Safety glasses
• Nitrile gloves
• Drain pan (at least 10-quart)
• 10mm socket
• Ratchet (3/8")
• 24mm socket
• Torque wrench (10-100 ft-lb range)
• Fluid transfer pump (specialty)
• OBD2 scan tool with transmission fluid 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 (Kia/Hyundai SP-IV compatible) - Qty: 6 quarts
• Transmission drain plug crush washer - Qty: 1
• Transmission fill/level plug crush washer - Qty: 1
• Brake cleaner - Qty: 1

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📋 Before You Begin

• Park on level ground and set the parking brake.
• Chock the rear wheels with wheel chocks.
• Warm the transmission with a short 10–15 minute drive so the fluid drains more completely.
• A crush washer is a soft sealing ring.
• A fluid transfer pump pushes ATF into a tight fill hole.
• A level/overflow plug sets the final fluid height.
• Assumption: Your transmission uses a drain plug, fill plug, and an overflow/level-set method (common on this Optima). If your case layout differs, follow the same concept: drain, refill, then level-set at temperature.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Lift and safely support the car

• Use a floor jack (rated 3-ton minimum) to lift the front of the car.
• Place jack stands (rated 3-ton minimum, pair) under solid front lift/support points.
• Make sure the car sits level (important for accurate fluid level).

Step 2: Remove the lower splash shield/undercover

• Use a 10mm socket and ratchet (3/8") to remove the fasteners.
• Set the shield and bolts aside so nothing gets lost.

Step 3: Identify the plugs and loosen the fill plug first

• Place your drain pan (at least 10-quart) under the transmission.
• Locate the fill plug on the transmission case (the one you’ll pump fluid into).
• Use a 24mm socket and ratchet (3/8") to crack the fill plug loose first (do not remove yet).
• Fill-first prevents being stuck empty.

Step 4: Drain the old transmission fluid

• Remove the drain plug using a 24mm socket and ratchet (3/8").
• Let the fluid drain until it becomes a slow drip.
• Measure how much came out (use markings on the drain pan or pour into a measured container).

Step 5: Reinstall the drain plug with a new crush washer

• Clean the plug area using shop rags and brake cleaner.
• Install a new transmission drain plug crush washer on the drain plug.
• Thread the drain plug in by hand first.
• Tighten with a torque wrench (10-100 ft-lb range): Torque to 49 Nm (36 ft-lbs).

Step 6: Refill with fresh ATF

• Remove the fill plug fully using the 24mm socket and ratchet (3/8").
• Use a fluid transfer pump (specialty) to pump in SP-IV compatible ATF.
• Add roughly the same amount you drained out as your starting point.
• Reinstall the fill plug finger-tight for now (you’ll be opening/closing during level-set).

Step 7: Level-set the fluid at the correct temperature

• Connect your OBD2 scan tool with transmission fluid temperature (specialty) and monitor transmission fluid temperature (TFT).
• Start the car (READY mode) and keep your foot on the brake.
• Move the shifter slowly through each position (P-R-N-D and back), pausing ~3 seconds in each.
• Let the transmission warm until TFT is about 50-60°C (122-140°F).
• If you can’t read TFT, use an infrared thermometer on the transmission pan as a rough backup (less accurate).
• With engine running, remove the level/overflow plug (or the designated level-check point) using the 24mm socket and ratchet (3/8").
• Correct level behavior:
  • If fluid runs out in a steady stream, let it drain until it becomes a thin drip.
  • If no fluid comes out, use the fluid transfer pump (specialty) to add ATF through the fill hole until it just starts to drip from the level opening.
• Install a new transmission fill/level plug crush washer if used on your plug design.
• Tighten plugs with a torque wrench (10-100 ft-lb range): Torque to 49 Nm (36 ft-lbs).

Step 8: Reinstall the undercover

• Reinstall the splash shield using the 10mm socket and ratchet (3/8").
• Snug the fasteners evenly (do not overtighten).

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✅ After Repair

• Start the car and check underneath for any leaks.
• Test drive 10–15 minutes, then recheck for leaks again on a clean surface.
• Shifts should feel smooth; any slipping or harsh shifting means stop driving and recheck fluid level.
• Dispose of used ATF properly at a local recycling/auto parts center.

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💰 DIY vs Shop Cost

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

DIY Cost: $60-$140 (parts only)

You Save: $110-$390 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?

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.