The GM Service Guy

GM is investigating an AWD malfunction affecting these three-row SUVs. Here's what triggers the warning, what the temporary fix is, and what to expect going forward.

A vibration that gets worse with speed and comes from underneath the truck, not the steering wheel, usually points to the driveshaft. Here's how to confirm it.

A whine that changes pitch with speed almost always points to the differential. Here's how to tell gear wear from bearing failure before it gets expensive.

Push the 4WD button and nothing happens, or a warning light flashes instead? The shift motor is the most common reason electronic transfer cases fail to engage.

Still common in the used GM truck and SUV fleet, the 6L80/6L90 has its own well-documented weak points. Here's what to watch for on a higher-mileage example.

A sudden "stuck in neutral" feeling at highway speed is the defining 9T65 complaint. Here's why it happens and what your options are.

Co-developed with Ford, the 10L80/10L90 is a complex, software-driven transmission. Here's how its most common complaints actually present and what fixes them.

Shudder on light acceleration, a hard 1-2 shift, or an unexpected downshift on the 8L90? Here's what's actually going on inside GM's 8-speed and what it costs to fix.