🔧 Colorado - Automatic Transmission Fluid Change

This job replaces the automatic transmission fluid in your Colorado to help maintain smooth shifting and protect the transmission. Your Colorado uses a sealed-style transmission service procedure, so fluid level is checked by temperature and a level plug—not by a dipstick.

Difficulty Level: Intermediate | Estimated Time: 2-3 hours

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⚠️ Safety & Precautions

• ⚠️ Support your Colorado safely on level ground. The truck must stay level for the fluid level check.
• ⚠️ Never work under a vehicle held only by a jack. Use jack stands.
• ⚠️ Transmission fluid gets hot. Wear gloves and safety glasses.
• ⚠️ Keep the engine running only during the final level check, with the parking brake set and wheels chocked.
• ⚠️ Used transmission fluid must be collected and recycled properly.

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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-quart minimum)
• Ratchet wrench 3/8-inch drive
• 10mm socket
• 15mm socket
• Torque wrench 3/8-inch drive
• Fluid transfer pump (specialty)
• Scan tool with transmission fluid temperature data (specialty)
• Infrared thermometer (optional)
• Plastic trim tool
• Shop towels

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Dexron-VI automatic transmission fluid - Qty: 6 quarts
• Automatic transmission filter kit - Qty: 1
• Automatic transmission pan gasket - Qty: 1
• Transmission drain plug seal - Qty: 1
• Transmission fill plug seal - Qty: 1

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📋 Before You Begin

• Park your Colorado on a flat, level surface.
• Set the parking brake and place wheel chocks behind the rear wheels.
• Let the transmission cool until it is safe to touch.
• A scan tool is needed to read transmission fluid temperature. This is important because fluid expands as it warms up.
• Do not disconnect the battery for this repair.
• Assumption: This procedure is for the factory automatic transmission in your Colorado.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Raise and Level the Truck

• Use the floor jack to lift your Colorado at the correct front lift point.
• Place jack stands under the frame rails.
• If needed, raise the rear with the floor jack and support it with jack stands so the truck sits level.
• Use wheel chocks to prevent movement.
• Level matters for accurate filling.

Step 2: Remove the Underbody Shield if Equipped

• Use a 15mm socket or 10mm socket to remove the underbody shield fasteners if your Colorado has one.
• Use a plastic trim tool to release any plastic retainers.
• Set the shield and hardware aside in order.

Step 3: Locate the Transmission Pan and Plugs

• Put on safety glasses and nitrile gloves.
• Place the drain pan under the transmission pan.
• Identify the transmission drain plug, fill plug, and level check plug before removing anything.
• The level check plug is used to confirm the correct amount of fluid when the transmission is warm.

Step 4: Remove the Fill Plug First

• Use the correct socket from your 3/8-inch ratchet wrench set to loosen the fill plug.
• Only loosen it at first. This proves you can refill the transmission before draining it.
• Replace the fill plug seal if it is damaged.
• Never drain before confirming refill access.

Step 5: Drain the Old Transmission Fluid

• Move the drain pan directly under the drain plug.
• Use the correct socket with the 3/8-inch ratchet wrench to remove the drain plug.
• Allow the fluid to fully drain until it slows to a drip.
• Clean the drain plug with shop towels.
• Install a new transmission drain plug seal.
• Reinstall the drain plug using the torque wrench 3/8-inch drive. Torque to 20 Nm (15 ft-lbs).

Step 6: Remove the Transmission Pan

• Keep the drain pan under the transmission.
• Use a 10mm socket to loosen the transmission pan bolts in a crisscross pattern.
• Leave a few bolts loosely installed at one end so the pan can tilt and drain safely.
• Support the pan with one hand and remove the remaining bolts using the 10mm socket.
• Lower the pan slowly because more fluid may spill.

Step 7: Replace the Transmission Filter

• Use a 10mm socket if the filter is bolted in place.
• Pull the old filter straight down by hand.
• A filter removes debris from the fluid before it circulates through the transmission.
• Make sure the old filter seal comes out with the filter.
• Install the new filter by pressing it straight into place.
• If filter bolts are used, tighten them with the torque wrench 3/8-inch drive. Torque to 10 Nm (89 in-lbs).

Step 8: Clean and Reinstall the Pan

• Clean the transmission pan with shop towels.
• Remove the old gasket from the pan sealing surface by hand or with a plastic trim tool.
• Do not scratch the metal sealing surface.
• Install the new automatic transmission pan gasket.
• Raise the pan into position and hand-start all bolts.
• Use a 10mm socket to snug the bolts evenly in a crisscross pattern.
• Use the torque wrench 3/8-inch drive. Torque pan bolts to 12 Nm (106 in-lbs).

Step 9: Add Initial Transmission Fluid

• Install the hose from the fluid transfer pump into the fill opening.
• Pump in Dexron-VI automatic transmission fluid until fluid begins to run back out of the fill opening.
• Install the fill plug loosely by hand.
• Do not final-tighten the fill plug yet.

Step 10: Warm the Transmission and Cycle Gears

• Connect the scan tool with transmission fluid temperature data.
• Start the engine while your Colorado is still level and safely supported.
• Press the brake pedal firmly.
• Move the shifter slowly through Park, Reverse, Neutral, Drive, and back to Park.
• Pause 3 seconds in each position.
• Watch transmission fluid temperature on the scan tool.

Step 11: Set the Final Fluid Level

• Keep the engine running.
• When transmission fluid temperature reaches the specified checking range, use the 3/8-inch ratchet wrench to remove the level check plug.
• For most GM sealed automatic transmissions, the fluid should be checked around 35-45°C (95-113°F).
• If no fluid comes out, use the fluid transfer pump to add Dexron-VI automatic transmission fluid through the fill opening until fluid dribbles from the level check opening.
• If a heavy stream comes out, let it drain until it becomes a thin dribble.
• Install the level check plug using the torque wrench 3/8-inch drive. Torque to 20 Nm (15 ft-lbs).

Step 12: Final-Tighten the Fill Plug

• Shut the engine off after the level check plug is installed.
• Install a new transmission fill plug seal if required.
• Use the torque wrench 3/8-inch drive to tighten the fill plug. Torque to 20 Nm (15 ft-lbs).
• Wipe the transmission pan and plug areas clean with shop towels.

Step 13: Reinstall the Underbody Shield

• Lift the underbody shield into place by hand.
• Use the 10mm socket or 15mm socket to reinstall the fasteners.
• Tighten the shield fasteners snugly. Do not overtighten plastic retainers.

Step 14: Lower the Truck

• Use the floor jack to raise your Colorado slightly off the jack stands.
• Remove the jack stands.
• Lower the truck slowly to the ground.
• Remove the wheel chocks.

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✅ After Repair

• ✅ Start your Colorado and let it idle for a minute.
• ✅ Shift through all gears again with your foot on the brake.
• ✅ Take a short, gentle test drive.
• ✅ Check under the truck for leaks at the pan, drain plug, fill plug, and level check plug.
• ✅ Recheck for leaks after the first full drive cycle.
• ✅ Dispose of used transmission fluid at a recycling center or auto parts store.

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💰 DIY vs Shop Cost

Shop Cost: $300-$550 (parts + labor)

DIY Cost: $90-$180 (parts only)

You Save: $210-$370 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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