April 2025 was LS month in the driveway. A GM truck had its engine pulled, the replacement was stripped down and stood up on the stand, and then it went back in. Our photo caption for the last shot says it in four words. Back in the truck.
The LS family of V8 engines is one of the most common swaps there is. Here is how one goes, and what makes the difference between a swap that runs right and one that keeps coming back.
Quick answer: An LS swap into a GM truck is common because the parts fit well. The work that decides how it runs is the prep. Clean surfaces, new seals, covered ports and matched sensors and wiring.
What We Saw
Why the LS Is Everywhere
GM put LS family V8s in millions of trucks and SUVs. That means used engines and parts are easy to find. It also means the mounts, the bell housing and the wiring in many GM trucks are already set up for one.
Easy to find does not mean ready to install. A used LS comes with someone else's history. So before it goes in, it gets looked at closely.
What Happens on the Stand
On the stand, the engine is easy to inspect and easy to clean. In our photos you can see the front of the block with the timing gear in view, and the intake ports taped over. Covering ports is a small step that matters. A bolt or a bit of grit in a port can end up in a cylinder.
- Look for oil and coolant leaks and fix the seals that are easy to reach now.
- Check the timing cover, rear main area and oil pan for seepage.
- Swap over the brackets, sensors and accessories that fit this truck.
- Make sure the knock sensors and their wiring are in good shape. They live in the valley under the intake on many of these engines.
Going Back In
The engine comes down on the hoist slowly, lined up with the transmission and mounts. Nothing gets forced. Once it is bolted in, the intake, wiring, fuel lines, cooling hoses and exhaust go back on in order.
Before the first start we check oil pressure and fluid levels. After it starts, we watch for leaks, check for codes and bleed the cooling system. Then it gets a test drive and a recheck when it is cool.
Questions Owners Ask About LS Swaps
Will a 5.3 from one truck fit another? Often, but not always. Sensors, wiring plugs, oil pans and accessory brackets changed over the years. We check before anything gets bought.
Does the computer need to change? Sometimes. The engine and the computer have to agree on things like the throttle and the cam sensor. We sort that out before install day.
Is a swap better than a rebuild? It depends on the engine you can get and how long you plan to keep the truck. We will lay out both.
What It Means for Your Truck
If your GM truck needs an engine, a used or rebuilt LS can be a good fix. Ask where it came from, what was checked and what the warranty covers. Also ask whether your truck's computer needs to be programmed for it.
We have done many of these since, in the driveway and now in our bays. See our engine repair page, our engine replacement cost guide, or the San Jacinto shop page.
Supercanic tip: Replace the rear main seal and oil pan gasket while a used engine is out. It is a small cost then and a big job later. Call or text (951) 644-1599.
Thinking About an Engine Swap?
Tell us the truck and the engine. We will tell you what it takes.
