What's the Difference Between an LS Swap and an LT Swap

People ask us this all the time. They've done an LS swap or they're planning one, and they want to know if LT is worth considering. Or they scored a deal on an LT engine and want to know what they're getting into.

The short answer is the LT swap isn't as different as most people think. One of our techs did an LT4 swap in his Chevelle and the process was similar to an LS swap in a lot of ways. There are a few key differences to understand, but it's not a completely different animal.

What Stays the Same

A lot of the swap is familiar if you've done LS work before.

The harness connections for injectors, knock sensors, and grounds are the same style. You're still dealing with drive by wire throttle. A Corvette pedal works with a PSI harness just like it does on an LS swap. Motor mounts, oil pans, headers, cooling, most of the mechanical side translates over but is not a direct fit.

If you can do an LS swap, you can do an LT swap. The learning curve isn't as steep as people make it sound.

Fuel System

This is the biggest difference and where most of the confusion comes from.

Factory Gen V LT engines use a pulse width modulated fuel pump. The ECM controls pump speed based on demand. Most of the information online makes it sound like PWM is the only way to run an LT engine. That's not true.

You can run a traditional fuel system with a constant-voltage pump and an adjustable regulator set to 73 PSI. We covered this in detail in our fuel system guide. The Tanks Inc Hellcat pump works great for LT applications. Pair it with an adjustable regulator, quality fuel line, and a PSI harness that supports traditional fuel delivery. No PWM controller needed.

This is how our tech runs his LT4 Chevelle. Traditional pump, adjustable regulator, no expensive PWM tank setup. Works great.

Fan Control

This one catches people off guard.

On an LS swap, the fans are controlled by the PCM through ground triggers. Two ground wires from the harness trigger the fan relays. Simple and straightforward.

On factory LT applications, GM switched to PWM controlled fans. The ECM controls fan speed the same way it controls the fuel pump. If you try to run factory fan control on an LT swap, you're dealing with that same PWM complexity.

The easier solution is to isolate the fan system entirely. Use a standalone fan controller like the Dakota Digital PAC-2800BT. It reads coolant temp and controls the fans independently from the ECM. No PWM wiring, no integration headaches. We sell it on the website.

This is how our tech set up his LT4 swap. Isolated fan control with the Dakota Digital unit. The ECM doesn't touch the fans.

If you want to run a factory style PWM fan, we recommend the C7 Corvette fan, or a SPAL PWM fan from Dewitts.

Just let us know which fan you are choosing so we can set it up correctly in the tune.

Tuning

Tuning an LT is different than tuning an LS.

The Gen V ECM requires more software credits to unlock and tune. The tools are more expensive and the process is more involved than a typical LS tune. If you're used to doing your own tuning with HPTuners on an LS, the LT side costs more to get into.

The solution is finding a good dyno shop that already has the licensing and experience with Gen V calibrations. They can handle the tune and you don't have to buy all the credits yourself. Budget for professional tuning on an LT swap.

Which One Should You Do

Depends on what engine you have access to and what your goals are.

LS engines are everywhere. Junkyards are full of 5.3s and 6.0s. Parts are cheap. Support is massive. If you're doing your first swap or want the easiest path, LS is still the move.

LT engines make more power in factory form and have more room for growth. The LT4 makes over 600 horsepower supercharged from the factory. If you want a modern powerplant with serious capability, LT is worth considering.

The swap process isn't that different. Fuel system, fan control, and tuning are the main things to plan around. Once you understand those, the rest is familiar.

Bottom Line

An LT swap isn't a completely different project from an LS swap. Same general process, same harness connector styles for most sensors, same drive by wire throttle setup.

The differences are fuel delivery, fan control, and tuning. All three can be handled without crazy complexity if you plan ahead.

We build harnesses for LT swaps that work with traditional fuel systems so you can skip the PWM setup. We sell the Dakota Digital fan controller to simplify fan wiring. And we can point you toward tuners who know Gen V calibrations.

If you're considering an LT swap and want to talk through the details, give us a call. We've done this and we can help you figure out what you need for your application.