The 2001 introduction of GM’s 6.6L LB7 Duramax diesel engine redefined what pickup trucks were capable of. The engine was the first heavy-duty pickup workhorse to use common-rail injection and aluminum cylinder heads, and it was both the most powerful and the quietest of the three main engines (Duramax, Cummins and Stroke) at the time.
Even such powerful perfection, however, could benefit from well-thought-out upgrades. The following are some of the best upgrades for LB7 Duramax engines.
Automatic Transmission
The original 6.6L LB7 Duramax was paired with both manual and automatic transmissions. The automatic option featured a commercial-grade five-speed from Allison Transmission, and this automatic provides long-term reliability so long as everything on the truck is stock. When upgrading the engine’s power, though, its output can overwhelm the automatic.
If you’re going to make any substantial upgrades that increase horsepower or torque, make sure to consult a diesel technician about upgrading the automatic transmission first. This is often one of the most essential upgrades for the LB7 Duramax engine, even though it’s not technically an upgrade to the engine block itself.
Fuel Injectors
The best upgrade for LB7 Duramax engines once they reach high mileage is replacing the fuel injectors. The stock injectors are infamous for their failures, and replacing these can both improve performance and increase long-term reliability. Even if the injectors won’t imminently fail, old injectors normally don’t perform optimally due to build-up that interferes with their fuel delivery.
Oversized Exhaust System
When an engine is upgraded so that it produces more power, it also generates more exhaust gases. Upgrade the stock exhaust system to a 4-inch downpipe-back exhaust system, and the aluminized exhaust will quickly usher away those burned-off gases. The result is improved airflow that allows the engine to take advantage of its full range of power.
Oversized Downpipe
If you’re having the transmission pulled to improve its performance, take the opportunity to change out GM’s standard downpipe with a higher-flowing one that’s 3 inches in diameter. Airflow will once again be improved, and power will be too. The downpipe is an easy and inexpensive upgrade if you already have the transmission out.
Aftermarket Fuel Supply
The 6.6L LB7 Duramax’s stock fuel system relies on a suction valve that pulls up fuel. While this system works fine from the factory, it’s doesn’t do as well once power — and fuel consumption — are increased. If you’re making substantial power upgrades, get an aftermarket fuel system that uses a lift pump to deliver fuel. This is absolutely necessary if your tuning requires an increased duration or injector on-time.