Home > Gen III LS / Vortec Harnesses
We have been building standalone wiring harnesses for the Gen 3 (24x - including the Gen IV 24x LS2) LS platform of engines since their inception.

We developed the first LS standalone wiring harness around 1996/1997 and have been building them in-house for thousands of automotive enthusiasts and professional companies around the world since then.

We build our LS swap harnesses on one of the many different live engine and transmission setups we have in-house which closely reflects the swap you are performing in your project at home or in the shop!

It is because of this process, our harnesses are the best running, looking, and fitting available.

The other major benefit of having us build your LS swap harness on one of our live engine and transmission setups is that we actually test run each and every harness we build prior to shipping. While your harness is running the engine, we have OEM GM diagnostic hardware and software hooked up to verify our work, and to help ensure trouble free operation once you receive the harness.

Once the LS swap harness has passed all of our diagnostic run tests, we cover it with our exclusive, heat resistant, woven fabric covering. This isn't a cheap see through plastic mesh covering, this is a nice quality covering and offers the correct fitting finish to your new Speartech harness that our customers expect.

The process and practices we choose to use takes a little more time, but we feel are necessary steps in order to ensure the end user has a good experience and gets something that "just works", and with proper installation, we know it will - we have already tested it on a live engine and transmission!

Put 23 years of GM Engineering experience - and now over 20 years spent perfecting the LS swap harness manufacturing process - to work for you!

We support all combinations of 1999+ Gen 3 (24x) LS / Vortec engines with any transmission including LS1, LS2, LS6, Vortec, etc.

All harnesses are built to order, and a full range of customization options are available to you. Whether you want your computer in the trunk, are running a supercharger or a "high ram" intake manifold, or any other aftermarket item that may change sensor/connector placements, etc., we can accommodate your customization requests. You don't have to run adapters or extensions, we build it just how you request it. We will create a custom harness layout draft and send it to you for approval before starting on your harness build if your project requires it.

Feel free to give us a call at (765) 378-4908 or email justin@speartech.com to discuss options, pricing, more info, or to get your Speartech harness build in the works! Our Gen 3 24x LS swap harness builds start at $750.

All harnesses include instructions, every wire labeled, and an OBD2 port with integrated check engine light for easy diagnostic checks down the road.

We can also handle your computer programming needs. Whether we are providing a programmed computer, or we are reprogramming one you supply, it will be tested together with your harness while running the engine!

If your LS swap harness doesn't require much customization, feel free to browse our harnesses below. You can fill out some quick information and place your Speartech harness order online. As always, feel free to give us a call prior to purchase with any questions you may have about our products. We are here to help!

Speartech - The Original and Still The Best!
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LS2 Gen 4 24x Harness
LS2 Gen 4 24x Harness
Our Price: $950.00

24x Gen 4 engines are found in the 05-06 GTO and TrailBlazer SS, as well as the 05 Corvette.

PCM shown for reference only. Not included with harness.
more info
LS1 / Vortec Harness - DBW Throttle
LS1 / Vortec Harness - DBW Throttle
Our Price: $850.00

Includes Vortec 4.8, 5.3, 6.0

Includes Pedal to TAC Module harness.

If you're sending in your PCM for reprogramming, use the "Special Notes" field above to let us know any engine modifications (headers, cam, etc.) and gear ratio and tire size.

PCM shown for reference only. Not included with harness.
more info
LS1 / Vortec Harness - Cable Throttle
LS1 / Vortec Harness - Cable Throttle
Our Price: $750.00

Includes Vortec 4.8, 5.3, 6.0

If you're sending in your PCM for reprogramming, use the "Special Notes" field above to let us know any engine modifications (headers, cam, etc.) and gear ratio and tire size.

PCM shown for reference only. Not included with harness.
more info
Vortec/4L60E (Drive By Wire) Standard Series Harness
Vortec/4L60E (Drive By Wire) Standard Series Harness
List Price: $599.99
Our Price: $495.00
Sale Price: $495.00
Savings: $104.99

We have a few harnesses available from a supplier that are ready to go off the shelf. These are not made in-house but we have fully labeled and test ran each one. Each harness has a diagnostic port (OBD2 port) with integrated check engine light (some may just have the wire for the check engine light). Setup by default for the LS2 MAF sensor.

These harnesses are not customizable like our Signature Series harnesses, which are built to order.

Pics are for reference of the harness itself and may not be specific to your application. We will ship the correct harness you order.
more info
Vortec/4L60E (Cable Throttle) Standard Series Harness
Vortec/4L60E (Cable Throttle) Standard Series Harness
List Price: $599.99
Our Price: $495.00
Sale Price: $495.00
Savings: $104.99

We have a few harnesses available from a supplier that are ready to go off the shelf. These are not made in-house but we have fully labeled and test ran each one. Each harness has a diagnostic port (OBD2 port) with integrated check engine light (some may just have the wire for the check engine light). Setup by default for the LS2 MAF sensor.

These harnesses are not customizable like our Signature Series harnesses, which are built to order.

Pics are for reference of the harness itself and may not be specific to your application. We will ship the correct harness you order.
more info
LS1/T56 (Cable Throttle) Standard Series Harness
LS1/T56 (Cable Throttle) Standard Series Harness
List Price: $599.99
Our Price: $495.00
Sale Price: $495.00
Savings: $104.99

We have a few harnesses available from a supplier that are ready to go off the shelf. These are not made in-house but we have fully labeled and test ran each one. Each harness has a diagnostic port (OBD2 port) with integrated check engine light (some may just have the wire for the check engine light). Setup by default for the LS2 MAF sensor.

These harnesses are not customizable like our Signature Series harnesses, which are built to order.

Pics are for reference of the harness itself and may not be specific to your application. We will ship the correct harness you order.
more info
LS1/4L60E (Cable Throttle) Standard Series Harness
LS1/4L60E (Cable Throttle) Standard Series Harness
List Price: $599.99
Our Price: $495.00
Sale Price: $495.00
Savings: $104.99

We have a few harnesses available from a supplier that are ready to go off the shelf. These are not made in-house but we have fully labeled and test ran each one. Each harness has a diagnostic port (OBD2 port) with integrated check engine light (some may just have the wire for the check engine light). Setup by default for the LS2 MAF sensor.

These harnesses are not customizable like our Signature Series harnesses, which are built to order.

Pics are for reference of the harness itself and may not be specific to your application. We will ship the correct harness you order.
more info
Cable-X Speedometer Adapter
Cable-X Speedometer Adapter
Our Price: $340.00

We carry the Cable-X Speedometer Adapter that allows you to retain your classic cable driven speedometer when using modern day electric VSS signal. This takes the VSS signal and converts it to a cable driven output to your gauge cluster/speedo, allowing your old cable driven speedo to work with an electronic VSS signal that modern transmissions use.
more info
GM LS-Series Engines: The Complete Swap Manual By Joseph Potak
GM LS-Series Engines: The Complete Swap Manual By Joseph Potak
List Price: $27.99
Our Price: $24.99
Sale Price: $24.99
Savings: $3.00

Here's the most helpful LSX swap book we've ever seen, and now available here on our site!

Stuffed full of info on identifying the different LS engines, helpful swap tips, PCM info, manifolds, oil pans, block differences, fuel systems, front accessory variations, transmissions, sensors, harnesses, cooling system plumbing tips, motor mounts, etc. It's all here!

Written by Joseph Potak, this book will guide you through every phase of your swap project using the number one most desired swap engine in the world!
more info
Firewall Harness Grommet
Firewall Harness Grommet
Our Price: $10.00

We get a lot of requests of customers wanting to buy the grommet we include with every new harness order, so we decided to make them available for purchase separately. Ideal for routing your harness through the firewall, etc. Sold individually. Free USPS shipping within the USA.

Drill a 2 1/8 inch hole for the grommet. Inside diameter where you pass wiring through is .6 inch and flexible (stretchy).

For free shipping at check out, select - More Carriers > Free USPS Shipping.
Grommets ship via USPS First Class only. We will adjust & refund accordingly if you're unable to select the free shipping option.
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