GM Wire Harness Modification & Repair
GM wire harness modification & repair
Reconfigure a donor LS or LT harness so the engine and transmission run correctly at full power — without building everything from scratch.
Modification service
What we need
The harness must come off the donor LT1, TPI, or LS1 (or related) engine undamaged. We reconfigure and tail out what you need to run the engine and transmission correctly, and the finished harness looks clean and new.
Builders use this service for sand rails, kit cars, off-road race rigs, street rods, and 4x4 trucks. You can place the modified harness wherever space allows.
If you have required lengths or drawings for an engine we already support, email them and we'll quote the extra work.
Built around your donor harness
What you gain
Lower cost and shorter wait than a full scratch-built Pro Wire Harness, with factory connectors that already fit your motor.
If you have mismatched sensors or parts, note them at quote time and we'll swap them for the quoted price. Note: on a factory donor harness we do not add trunk length. If you need a longer harness, see Pro Wire Harness for a from-scratch build sized to your measurements.
Straightforward pricing
Pricing
Modification service starts at $600 plus shipping.
This work typically takes more than 40 hours of harness work plus operating-system programming — that's why we don't discount below that floor.
Start a modification build
Tell us about your donor harness, engine, transmission, and vehicle.
Start a build