🔧 GLA - Transmission Fluid Change

Your GLA’s dual-clutch transmission (DCT) fluid needs to be drained and refilled at a specific fluid temperature and with the car perfectly level. Doing it correctly helps clutch life, shift quality, and prevents over/under-filling.

Difficulty Level: Advanced | Estimated Time: 2.5-4.0 hours

Assumption: Your GLA has the 7-speed DCT (7G-DCT) and is stock.

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⚠️ Safety & Precautions

• ⚠️ Work on a level surface; the fluid level is temperature- and level-sensitive.
• ⚠️ Exhaust and transmission case can be very hot; wear gloves and let it cool if needed.
• ⚠️ Use jack stands; never rely on a floor jack alone.
• ⚠️ Keep the engine running only when instructed; keep hands/clothes away from the belt and fans.
• ⚠️ No battery disconnect is required for a fluid service, but keep the key away from the car when underneath to prevent accidental start.

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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 (10-liter minimum)
• Fluid transfer pump (specialty)
• Mercedes-capable scan tool with transmission oil temperature PID (specialty)
• Torx T25 screwdriver
• Torx T30 screwdriver
• E-Torx E10 socket
• 8mm socket
• 10mm socket
• Ratchet (3/8")
• Torque wrench (5–60 Nm range)
• Trim clip tool
• Brake cleaner spray
• Shop towels

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• DCT transmission fluid (MB-approved for 7G-DCT, MB 236.21/236.22 equivalent) - Qty: 8 quarts
• Transmission fluid filter kit - Qty: 1
• Transmission pan gasket - Qty: 1
• Drain plug sealing ring - Qty: 1
• Fill plug sealing ring - Qty: 1

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📋 Before You Begin

• Park on a level surface, set the parking brake, and chock the rear wheels.
• Raise the front and support with jack stands under proper lift points; keep the car level front-to-rear.
• Set up your scan tool so you can read transmission oil temperature (this is the live temperature value used for final level setting).
• Lay out cardboard and towels; DCT fluid is slippery and messy.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the lower underbody cover

• Use a Torx T25 screwdriver and 8mm socket to remove the fasteners holding the front undertray.
• Use a trim clip tool for any plastic push-clips.
• Set hardware aside in a small tray so you don’t lose it.

Step 2: Locate the DCT drain and fill points

• Identify the transmission oil pan area and the drain plug at the lowest point.
• Identify the fill/level plug (the plug used to set final level). Always loosen the fill plug first.

Step 3: Loosen the fill/level plug first

• Place the drain pan under the transmission.
• Use the correct socket/bit (commonly E-Torx E10 socket depending on plug style) to crack the fill/level plug loose.
• If it won’t loosen, stop here—don’t drain the transmission if you can’t refill it.

Step 4: Drain the old transmission fluid

• Use the correct socket/bit (commonly E-Torx E10 socket depending on plug style) to remove the drain plug.
• Let it drain until it becomes a slow drip.
• Clean the area with shop towels and brake cleaner spray.

Step 5: Remove the pan and replace the filter

• Use an E-Torx E10 socket and ratchet to remove the transmission pan bolts.
• Lower the pan carefully; more fluid will spill into the drain pan.
• Remove the old filter using an E-Torx E10 socket (fastener style varies) and install the new filter from your kit.
• Install the new pan gasket and reinstall the pan.
• Torque to 8 Nm (71 in-lbs) for the pan bolts (tighten in a crisscross pattern).
• Do not over-tighten—pan bolts strip easily.

Step 6: Install drain plug with a new sealing ring

• Install a new drain plug sealing ring on the drain plug.
• Thread in by hand first to avoid cross-threading.
• Use a torque wrench to tighten the drain plug.
• Torque to 20 Nm (15 ft-lbs).

Step 7: Fill with the correct DCT fluid (initial fill)

• Install a new fill plug sealing ring on the fill/level plug (if it uses one).
• Use a fluid transfer pump (specialty) to pump DCT fluid into the fill port until it begins to run back out.
• Reinstall the fill/level plug finger-tight for now.

Step 8: Run the transmission and cycle gears

• Lower the car enough that it’s safely supported and level, with wheels off the ground if possible.
• Start the engine and keep your foot on the brake.
• Slowly move the shifter through P-R-N-D, pausing 3–5 seconds in each position, then back to P.
• This circulates fluid through the clutch and valve body circuits.

Step 9: Set the final fluid level at the correct temperature

• With the engine running, use your Mercedes-capable scan tool (specialty) to read transmission oil temperature.
• When the transmission oil is at 45°C (113°F), remove the fill/level plug using the correct socket/bit.
• If no fluid dribbles out, use the fluid transfer pump (specialty) to add fluid until a steady dribble starts.
• Once it becomes a slow drip, install the fill/level plug.
• Torque to 20 Nm (15 ft-lbs).
• The “slow drip” is the correct level indication.

Step 10: Reinstall underbody cover

• Reinstall the undertray using a Torx T25 screwdriver, Torx T30 screwdriver, and 8mm socket as equipped.
• Tighten snugly; small fasteners typically do not require high torque.

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✅ After Repair

• With the engine running, inspect the drain and fill areas for leaks using a flashlight and shop towels.
• Road test 10–15 minutes: check for smooth takeoff and normal shifting.
• Recheck for leaks after the test drive.
• If your scan tool supports it, perform a transmission adaptation reset/relearn only if you had shift quality issues; otherwise, it’s usually not required after routine service.

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💰 DIY vs Shop Cost

Shop Cost: $450-$900 (parts + labor)

DIY Cost: $140-$320 (parts only)

You Save: $310-$580 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2.0-3.0 hours.

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🎯 Ready to get started?

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