GM

The LLY brought a variable-geometry turbo to GM’s 6.6L diesel. Its RPO spans an important hardware transition: the familiar 2004.5–2005 pickup and the later 2006/van versions need different controller and parts identification.

The LL8’s smooth inline-six and aluminum DOHC design powered the Envoy and its GM relatives. Its RPO stayed the same through several revisions, but horsepower and controllers changed—one rating does not cover every model year.

The LU3 is the familiar workhorse V6 behind many basic GM pickups and vans. Its iron construction, pushrod valve gear and port injection keep it mechanically straightforward, but age-related ignition and fuel-system faults deserve more attention than its modest power rating.

The L18 delivers its appeal at low rpm: big displacement and strong naturally aspirated torque. It is a big-block engine, with its own parts and control-system requirements rather than small-block interchangeability.

The iron-block 6.0L is the heavy-duty branch of GM’s early LS-based truck engines. LQ4 does the hauling, while the higher-compression LQ9 appears in selected performance and luxury applications.

GM’s 5.3L Vortec balances everyday torque with a simple port-injected V8 layout. LM7, flex-fuel L59 and aluminum-block L33 look similar, but fuel compatibility and hardware identification matter when buying an engine or controller.

The LR4 gives GM’s entry-level V8 trucks a compact, durable small-block foundation. It has conventional port injection and eight active cylinders, with no factory AFM system to diagnose.