GMC Sierra T1XX (2019-Present) transmission slips when accelerating, what to do

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

Solution

1. Preparation

• Gather required tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is turned off.
• Disconnect the battery to prevent electrical issues.

2. Check and Replace Transmission Fluid

1. Drain Old Fluid

   • Locate the transmission pan and place a drain pan underneath.
   • Remove the drain plug or pan bolts and drain the old fluid completely.
   • Tools: Socket set, drain pan.

2. Inspect Fluid Condition

   • Check the fluid for metal shavings or burnt smell. If it appears contaminated, further inspection is required.

3. Replace Filter

   • Remove the transmission pan completely and clean the mating surfaces.
   • Replace the transmission filter according to manufacturer's specifications.
   • Tools: Socket set, gasket scraper, new transmission filter.

4. Install New Gasket and Pan

   • Apply a new gasket or sealant as needed and reattach the transmission pan.
   • Torque bolts to the manufacturer's specifications.
   • Tools: Torque wrench.

5. Refill Transmission Fluid

   • Refill with the correct type and amount of transmission fluid as per the owner’s manual.
   • Tools: Funnel.

3. Replace Transmission Control Module (if necessary)

1. Remove TCM

   • Locate the TCM, typically found near the transmission or under the dashboard.
   • Disconnect the electrical connectors and remove mounting bolts.
   • Tools: Socket set.

2. Install New TCM

   • Position the new TCM and secure it with bolts, then reconnect electrical connectors.
   • Tools: Socket set.