Speartech STE-LS3-6L80 LS3 6L80 Standalone Wiring Harness Kit Gen 4 LS Swap

The Speartech STE-LS3-6L80 is a purpose-built, standalone wiring harness kit designed for Gen 4 LS3 engine swaps paired with the 6L80 or 6L90 six-speed automatic transmission. Built to order and tested on a live engine and transmission before shipping, this harness delivers a true plug-and-play installation experience for hot rod builders, restomod enthusiasts, and professional shops.

Speartech pioneered the Gen 4 LS standalone swap harness and was among the first to develop 6L80/6L90 transmission integration for swap applications. Every harness is constructed in-house and finished with an exclusive heat-resistant woven fabric covering for a clean, professional appearance under the hood.

Kit Includes:

• Engine main wiring harness with fully labeled connectors and hook-up wires
• Transmission main harness compatible with 6L80 / 6L90
• Engine ECU (E38) and Transmission Control Module (T43 TCM, if applicable)
• MAF sensor with bung
• EVAP canister
• Pre-cat and post-cat oxygen sensors
• Drive-by-wire (DBW) throttle pedal
• OBD2 port with integrated check engine light for diagnostics
• Fuse block, relays, and firewall harness grommet
• Printed installation instructions

Key Features:

• Plug-and-play design — compatible with all engine, transmission, and emissions control sensors
• Built to order — fully customizable harness layout including ECM placement, supercharger provisions, high-ram intake accommodations, and more
• Emissions wiring options — harnesses come standard without post-cat O2s, purge, or EVAP; emissions wiring available as an add-on
• A/C compatible — selectable air conditioning support for GM A/C compressor setups
• Tap Shift ready — optional 6L80/6L90 tap shift module integration available
• Every wire labeled — simplifies installation and future diagnostics
• Heat-resistant woven fabric covering — professional finish and added protection
• Tested on a live engine and transmission prior to shipment

The STE-LS3-6L80 supports all Gen 4 LS 58x engine variants including the LS3, L99, LS7, LSA, LS9, and 5.3/6.0/6.2 Vortec truck engines when paired with the 6L80 or 6L90 transmission. Custom harness layout drafts are available for complex builds prior to production.