GMC Sierra T1XX (2019-Present) transmission slipping when shifting what to do

GMC Sierra T1XX (2019-Present)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

3 min read

550 words

⚠️ Safety Warning

This issue requires immediate attention. If you are not experienced with automotive repairs, consult a professional mechanic. Working on critical systems can be dangerous.

Problem Statement

Learn how to diagnose and fix transmission slipping issues in GMC Sierra T1XX (2019-Present). Step-by-step guide with symptoms and repair instructions.

Affected Component

Transmission

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems.
•Allow the engine to cool before opening the transmission pan.

Symptoms

•Check engine light illuminated
•Delayed or harsh shifting between gears
•Engine RPMs increasing without corresponding vehicle speed
•Fluid leaks under the vehicle
•Burning smell from transmission fluid
•Erratic or unpredictable transmission behavior

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to identify any transmission-related codes.
2
Inspect the transmission fluid level and condition; check for signs of contamination or burning.
3
Examine the transmission connections and wiring for any visible damage or loose connections.
4
Test the transmission fluid pressure using a pressure gauge to ensure it meets manufacturer specifications.
5
Assess the condition of the transmission filter and solenoids for proper operation.
6
Road test the vehicle to replicate the slipping condition and note the circumstances under which it occurs.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Socket set
•Torque wrench
•Drain pan
•Funnel
•Multimeter

Parts Required

•Transmission fluid (Dexron VI or as specified)
•Transmission filter
•Gasket for transmission pan
•Transmission solenoids (if needed)

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Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to identify any transmission-related codes.
2
Inspect the transmission fluid level and condition; check for signs of contamination or burning.
3
Examine the transmission connections and wiring for any visible damage or loose connections.
4
Test the transmission fluid pressure using a pressure gauge to ensure it meets manufacturer specifications.
5
Assess the condition of the transmission filter and solenoids for proper operation.
6
Road test the vehicle to replicate the slipping condition and note the circumstances under which it occurs.

Solution

1. Preparation

Gather tools and parts required for the repair.
Disconnect the negative battery terminal to prevent electrical shorts.
Allow the vehicle to cool if it has been running.

2. Fluid Change

Sub-steps:
1. Raise the vehicle using jack stands and secure it.
2. Place a drain pan under the transmission pan.
3. Remove the transmission pan bolts using a socket set and carefully lower the pan, allowing fluid to drain completely.
4. Replace the transmission filter by unbolting it and installing the new filter, ensuring the O-ring is seated correctly.
5. Clean the transmission pan and replace the gasket with a new one.
6. Reinstall the transmission pan and torque the bolts to manufacturer specifications (typically around 10-12 ft-lbs).

3. Fluid Replacement

Sub-steps:
1. Using a funnel, refill the transmission with the recommended fluid type (usually Dexron VI or as specified in the owner’s manual).
2. Start the engine and allow it to reach operating temperature.
3. Check the fluid level with the engine running and add fluid as necessary until it reaches the correct level.

4. Electrical Component Inspection

Sub-steps:
1. Inspect the transmission wiring harness for wear or damage.
2. Use a multimeter to check the resistance of the solenoids and ensure they are functioning within manufacturer specifications.
3. Replace any faulty solenoids or damaged wiring as needed.