my GMC Sierra T1XX (2019-Present) has difficulty shifting gears, what should I check?

GMC Sierra T1XX (2019-Present)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

3 min read

589 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 shifting issues in GMC Sierra T1XX (2019-Present). Step-by-step guide with diagnostic procedures 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 fluid reservoir.

Symptoms

•Hard or delayed shifting between gears
•Slipping transmission (engine revs but vehicle speed doesn't increase)
•Unusual noises (grinding or whining) during gear changes
•Dashboard warning lights illuminated (e.g., check engine light)
•Fluid leaks under the vehicle

Diagnostic Steps

1
Check the transmission fluid level and condition using the dipstick.
2
Scan the vehicle's onboard diagnostic system for any error codes using an OBD-II scanner.
3
Inspect the transmission linkage for proper adjustment and any visible damage.
4
Examine the transmission fluid for contamination or burnt smell.
5
Test the battery voltage and alternator output to ensure adequate power supply to transmission solenoids.
6
Inspect the vehicle’s engine mounts for wear or damage that could affect shifting.

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
•Fluid catch pan
•Transmission dipstick
•Funnel
•Multimeter

Parts Required

•Transmission fluid (specific to GMC Sierra)
•Transmission filter (if applicable)
•Gasket for transmission pan (if applicable)

Related Faults

Share this solution

Comments

No comments yet

Be the first to share your thoughts

Back to Generation

Diagnostic Steps

1
Check the transmission fluid level and condition using the dipstick.
2
Scan the vehicle's onboard diagnostic system for any error codes using an OBD-II scanner.
3
Inspect the transmission linkage for proper adjustment and any visible damage.
4
Examine the transmission fluid for contamination or burnt smell.
5
Test the battery voltage and alternator output to ensure adequate power supply to transmission solenoids.
6
Inspect the vehicle’s engine mounts for wear or damage that could affect shifting.

Solution

1. Preparation

Tools Required: OBD-II scanner, socket set, fluid catch pan, transmission dipstick, funnel.
Ensure the vehicle is parked on a level surface and the parking brake is engaged.
Disconnect the battery to ensure safety.

2. Check and Replace Transmission Fluid

Sub-steps:
1. Locate the transmission dipstick and remove it.
2. Check the fluid level and condition; if low or burnt, proceed to replace.
3. Drain the old fluid by removing the transmission pan bolts and allow fluid to completely drain into a catch pan.
4. Clean the transmission pan and replace the filter if necessary (consult manual for specific filter replacement).
5. Reinstall the pan with new gasket and torque bolts to manufacturer's specifications (usually around 10-15 ft-lbs).
6. Fill with new, manufacturer-recommended transmission fluid using a funnel until proper level is reached.

3. Inspect and Adjust Transmission Linkage

Sub-steps:
1. Locate the transmission linkage and inspect for damage or misalignment.
2. Adjust the linkage as necessary, ensuring it moves freely and engages properly.
3. Tighten any loose bolts and ensure everything is secure.

4. Scan and Address Fault Codes

Sub-steps:
1. Connect the OBD-II scanner to the vehicle’s diagnostic port.
2. Retrieve any error codes and document them.
3. Research codes to determine the specific issue (e.g., solenoid malfunction, sensor failure).
4. Replace any faulty components as indicated by the error codes.

5. Battery and Alternator Check

Sub-steps:
1. Use a multimeter to check the battery voltage (should be around 12.6 volts when off).
2. Test the alternator output while the engine is running (should be between 13.8 and 14.4 volts).
3. Replace the battery or alternator if readings are outside the normal range.