List of Problems with GM 6.6L Gas Engine

The GM gas 6.6L engine (L8T) has some problems reported by owners like:

  • Knocking noise
  • Random tick sound
  • Bad lifters and valve springs
  • Valve noise
  • High gas usage


Note that owners have reported that GM has fixed most of the problems after taking it in.


Here is what people like about it:

  • Large towing capacity
  • Solid
  • Smooth
  • Good MPG
  • Direct injected

It is GM’s gen 5 small block engine used in Silverado and Sierra HD.  It has 401 horsepower, 464 lb-ft torque, uses regular gasoline, 2 valves per cylinder.

The previous engine was the L96 with: 360 hp, 380 lb-ft torque.