GMC Sierra T1XX (2019-Present) transmission slipping when shifting what should I check

GMC Sierra T1XX (2019-Present)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

3 min read

531 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, diagnostics, and repair instructions.

Affected Component

Transmission

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect battery before working on electrical systems.
•Allow engine and transmission to cool before opening components.

Symptoms

•Transmission slips during acceleration
•Delayed engagement when shifting from park to drive
•Unusual noises during shifting
•Check engine light illuminated
•Poor fuel economy
•Fluid leaks under the vehicle

Diagnostic Steps

1
Check for any stored trouble codes using an OBD-II scanner.
2
Inspect the transmission fluid level and condition (color and smell).
3
Look for external leaks around the transmission and seals.
4
Verify the operation of the transmission control module (TCM).
5
Examine the transmission filter for clogs or restrictions.
6
Test the transmission solenoids for proper function.

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
•Transmission funnel
•Drain pan
•Multimeter
•Gasket scraper

Parts Required

•Transmission fluid (manufacturer-recommended type)
•Transmission filter
•Gasket for transmission pan
•Transmission solenoids (if faulty)

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Diagnostic Steps

1
Check for any stored trouble codes using an OBD-II scanner.
2
Inspect the transmission fluid level and condition (color and smell).
3
Look for external leaks around the transmission and seals.
4
Verify the operation of the transmission control module (TCM).
5
Examine the transmission filter for clogs or restrictions.
6
Test the transmission solenoids for proper function.

Solution

1. Preparation

Gather all necessary tools and parts.
Ensure the vehicle is on a level surface and secure with jack stands if elevated.
Disconnect the battery to avoid electrical shorts.

2. Check and Replace Transmission Fluid

Sub-steps:
1. Remove the transmission dipstick and check fluid level.
2. If low, add the manufacturer-recommended transmission fluid.
3. If fluid is discolored or burnt, drain the old fluid.
4. Replace with new transmission fluid, ensuring proper amount is added.
Tools Required: Transmission funnel, fluid pump, drain pan.

3. Inspect and Replace Transmission Filter

Sub-steps:
1. Remove the transmission pan using a socket set (note torque specs for reinstallation).
2. Remove the old filter and inspect for debris.
3. Install the new filter, ensuring it is seated properly.
4. Clean the transmission pan and reinstall it with a new gasket.
Tools Required: Socket set, gasket scraper.
Safety Warnings: Allow the transmission fluid to cool before handling.

4. Test and Replace Transmission Solenoids (if necessary)

Sub-steps:
1. Locate the transmission solenoids, typically found on the valve body.
2. Disconnect the electrical connectors and remove the solenoids.
3. Test solenoids for resistance using a multimeter.
4. Replace any faulty solenoids with new parts.
Tools Required: Multimeter, socket set.

5. Reconnect Battery and Test Drive

Sub-steps:
1. Reconnect the battery terminals.
2. Start the vehicle and allow it to come to operating temperature.
3. Perform a test drive to assess shifting behavior.
Tools Required: None.