🔧 K900 - Transmission Fluid Drain & Fill

This service replaces the old automatic transmission fluid (ATF) by draining what’s in the pan and refilling to the correct level at a specific fluid temperature. Getting the level right matters because too little can cause slipping, and too much can cause foaming and harsh shifting.

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

Assumption: Your K900 uses an 8-speed RWD automatic with a fill plug and a temperature-based level check.

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⚠️ Safety & Precautions

• ⚠️ Work on a level surface and support the car with jack stands before going underneath.
• ⚠️ ATF can be hot. Wear gloves and safety glasses and let components cool if needed.
• ⚠️ Keep the car stable: use wheel chocks and never rely on a jack alone.
• ⚠️ Engine may need to run during final level check—keep hands/clothes away from moving parts.

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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)
• Socket set 10mm-24mm
• Ratchet
• Torque wrench (10-100 Nm range)
• Hex bit socket set (5mm-10mm)
• Trim clip removal tool
• Fluid transfer pump (specialty)
• OBD2 scan tool with live data (specialty)
• Shop rags
• Brake cleaner spray

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Automatic transmission fluid (Kia/Hyundai SP-IV equivalent) - Qty: 6 quarts
• Transmission drain plug crush washer - Qty: 1
• Transmission fill plug crush washer - Qty: 1

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📋 Before You Begin

• Park on level ground, set the parking brake, and place wheel chocks at the rear wheels.
• Raise the front with a floor jack and support with jack stands at the proper lift points; keep the car level (front-to-rear) for accurate fluid level.
• Locate your scan tool’s transmission fluid temperature PID. You’ll use it later to set the final level.
• A transfer pump pushes fluid upward into the fill hole.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the lower undercovers

• Use a 10mm socket and trim clip removal tool to remove the splash shield/undercovers under the transmission area.
• Set all bolts/clips aside in a tray so nothing is lost.

Step 2: Identify the fill plug BEFORE draining

• Find the transmission fill plug (typically on the side of the case).
• Use the correct size from your socket set 10mm-24mm or hex bit socket set to loosen it slightly, then snug it back.
• If you can’t open the fill plug, don’t drain.

Step 3: Drain the old ATF

• Position a drain pan (at least 10-quart) under the transmission drain.
• Remove the drain plug using the appropriate tool from your socket set 10mm-24mm or hex bit socket set.
• Let it drain until it slows to a drip.
• Clean the drain plug area with shop rags and brake cleaner spray.

Step 4: Reinstall the drain plug (with new washer)

• Install a new transmission drain plug crush washer on the drain plug.
• Thread the drain plug in by hand first (to avoid cross-threading), then tighten with a ratchet.
• Torque to 39 Nm (29 ft-lbs) using a torque wrench.

Step 5: Refill with new ATF (initial fill)

• Remove the fill plug using the correct tool from your socket set 10mm-24mm or hex bit socket set.
• Use a fluid transfer pump (specialty) to pump in ATF (Kia/Hyundai SP-IV equivalent).
• Add roughly what came out (many drain & fills are about 4-5 quarts), plus a little extra to begin the level-setting process.
• Install a new transmission fill plug crush washer, then reinstall the fill plug finger-tight for now.

Step 6: Warm the fluid and circulate it

• Connect your OBD2 scan tool with live data (specialty) and monitor transmission fluid temperature.
• Start the engine and keep your foot firmly on the brake.
• Slowly move the shifter through P-R-N-D and back, pausing ~3 seconds in each position to circulate fluid.
• Leave the engine idling while you proceed to the level check.

Step 7: Set the final fluid level (temperature-based)

• With the engine idling, watch the scan tool and aim for 50°C-60°C (122°F-140°F).
• There are 2 common level-check styles—use the one your transmission has:

• Style A: Overflow/standpipe inside the drain (common on many Kia/Hyundai)
• Use the correct hex bit socket to remove the small level/overflow plug (center plug) if equipped.
• Correct level: a thin stream/dribble comes out at the target temperature.
• If nothing comes out, add ATF through the fill hole using the fluid transfer pump (specialty) until it dribbles.
• When it becomes a light drip, reinstall the overflow plug and torque to 10 Nm (7 ft-lbs).

• Style B: Side level plug
• Use the correct tool from your socket set 10mm-24mm or hex bit socket set to remove the level plug.
• Correct level: a small steady trickle at the target temperature.
• If low, add ATF through the fill hole with the fluid transfer pump (specialty) until it trickles from the level hole.
• Reinstall the level plug and torque to 39 Nm (29 ft-lbs).

Step 8: Final-tighten the fill plug

• Shut the engine off.
• Tighten the fill plug with a torque wrench.
• Torque to 39 Nm (29 ft-lbs).
• Clean any spilled fluid using shop rags and brake cleaner spray.

Step 9: Reinstall undercovers and lower the car

• Reinstall undercovers using the 10mm socket and trim clip removal tool.
• Lower the car safely using the floor jack and remove jack stands.

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✅ After Repair

• Start the engine and check underneath for leaks around the drain/fill/level plugs.
• Test drive 10-15 minutes, then re-check for leaks on a clean, dry surface.
• Confirm shifting feels normal (no flare/slip/harsh engagement).
• Wipe everything clean so leaks are obvious later.

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💰 DIY vs Shop Cost

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

DIY Cost: $60-$120 (parts only)

You Save: $190-$330 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.