GMC Repair & Service in San Marcos, Texas

About GMC Service at Riley Auto Care

GMC builds professional-grade trucks and SUVs designed for drivers who demand capability without sacrificing refinement. The Sierra, Yukon, and Yukon XL are among the most capable and well-appointed vehicles in their class, and they require service from a shop that understands their engineering. Riley Auto Care & Transmissions has extensive experience with the full GMC lineup and provides the expert care these vehicles deserve.

GMC's 5.3L and 6.2L V8 engines — shared with Chevrolet — are powerful and durable but are susceptible to Active Fuel Management (AFM) and Dynamic Fuel Management (DFM) lifter failures. This is one of the most common issues we see in Sierra and Yukon owners, and we can perform lifter replacements or disable the AFM/DFM system entirely to prevent recurring problems. We also specialize in the 6L80 and 8L90 automatic transmissions, providing fluid services, solenoid repairs, and complete rebuilds.

As HP Tuners certified technicians, we can recalibrate your GMC's engine and transmission control modules for improved towing performance, throttle response, or fuel economy. For Sierra HD owners with the Duramax diesel, we provide diesel-specific maintenance including EGR service, fuel system cleaning, and DPF care. Serving GMC drivers throughout the region, we deliver the professional-grade service your truck was built to receive.