The LS swap is one of the most popular engine swaps in the hobby. Behind it, you need the right transmission. Here's the complete guide to picking and installing the right trans behind your LS engine.
Top transmission choices behind LS
4L60E (most common, easiest)
- 4-speed automatic with overdrive
- Direct bolt-up to most LS engines
- Wide aftermarket support
- Cheap to rebuild
- Adequate for stock to mild performance
- Best for: Daily drivers, mild performance, budget builds
4L80E (HD option)
- 4-speed automatic with overdrive
- Bolts up to LS with adapter or direct (some LS variants)
- Much stronger than 4L60E
- More expensive to rebuild
- Better for HD use and high HP
- Best for: Tow rigs, performance builds, high HP applications
6L80 (modern automatic)
- 6-speed automatic
- Direct bolt-up to LS in factory applications
- Newer design, better fuel economy
- More complex electronics
- Limited aftermarket support compared to older trans
- Best for: Modern LS swap applications, daily drivers wanting modern feel
T56 / Tremec TR-6060 (manual)
- 6-speed manual
- Bolt-up requires bellhousing/adapter for LS
- Race-proven, strong
- Aftermarket support strong
- Best for: Performance / race applications, manual purists
Tremec Magnum / TKO (manual)
- 5-speed or 6-speed manual
- Aftermarket performance options
- Strong for LS-powered applications
- Best for: Performance manual swaps
What to use by application
Street rod / restomod (stock LS)
- 4L60E or 700R4 (older swap)
- Stock-power LS easy on either
- Quality rebuilt: $1,500-2,500
Daily driver / mild performance (LS swap into 1990s+ Chevy)
- 4L60E - the easy choice
- Wide parts availability
- Quality rebuilt: $1,500-3,000
Performance build (LS swap, cam, headers, 400+ HP)
- 4L60E with Sonnax billet input + HD frictions
- Or 4L80E for more headroom
- Quality build: $3,000-6,000
High HP / built engine (LS swap, 500+ HP)
- 4L80E (mandatory)
- Built with HD components throughout
- $5,000-9,000 typical
Race / drag build (LS swap, 600+ HP)
- 4L80E or TH400 (purists)
- Race-spec build
- $8,000-15,000
Stock LS in 1995-2010 GM truck
- 4L60E or 4L65E (factory)
- Just rebuild what's there
- $2,000-3,500
LS swap into older muscle car (1970s+ Chevelle, Camaro, etc.)
- 4L60E + adapter
- Or stay with TH350/TH400 with adapter
- Or go manual with T56
Bolt-up considerations
Direct bolt-up to LS:
- 4L60E (most years)
- 4L65E
- 4L70E
- 4L80E (some applications)
- 6L80 (factory LS applications)
- 8L90 (factory)
Requires adapter:
- TH350 → adapter needed
- TH400 → adapter needed
- 700R4 → adapter needed
- T56 → adapter and bellhousing
- Older manuals → various adapter needs
Adapter costs:
- TH350/400 adapter: $80-150
- 700R4 adapter: $50-100
- T56 adapter and bellhousing: $300-700
- LS-to-old-pattern adapter: $50-200
Wiring considerations
Stand-alone TCM (recommended for swaps)
- TCM specifically designed for swap applications
- Examples: Compushift, US Shift, BMP, Lokar
- Handles all trans control without needing factory ECM
- Cost: $400-700
Use factory ECM/TCM
- Requires correct ECM/TCM for your trans + engine combo
- Wiring is more complex
- Cost: variable
Manual lockup only (cheapest)
- Driver-controlled TCC
- Doesn't address electronic shifts (4L60E needs TCM)
- Cost: $30-100
What you need for each trans:
4L60E electrical needs:
- TCM (stand-alone or factory)
- VSS (vehicle speed sensor)
- TPS signal
- Brake switch
- TCC solenoid wiring
- Shift solenoid wiring
4L80E electrical needs:
- TCM (stand-alone or factory)
- VSS
- TPS signal
- Brake switch
- Solenoid pack wiring
- More complex than 4L60E
6L80 electrical needs:
- Most complex of all
- Requires specific TCM or capable stand-alone
- Many sensor inputs
- Verify with installer before swap
Torque converter selection
LS swap torque converter considerations:
- Match stall to engine torque peak
- Stock LS torque peak: ~4,200 RPM
- Cammed LS torque peak: ~5,000-5,800 RPM
- Stall should be 400-500 RPM below torque peak for street
LS-specific converters:
- Manufacturers offer LS-specific designs
- Goerend, BMP, Yank, ATI, TCI all have options
- Cost: $400-1,500 depending on grade
Stock-stall for stock LS:
- 1,800-2,200 RPM
- $300-500 quality unit
Performance stall for cammed LS:
- 2,400-3,200 RPM
- $500-1,000 quality unit
Race stall for built LS:
- 3,200-4,500 RPM
- $1,000-2,000 race-spec unit
Flexplate considerations
LS-specific flexplate:
- LS has its own flexplate pattern
- Standard 168-tooth typical
- Cost: $80-200
Internal balance:
- All LS engines are internally balanced
- No need for external balance flexplate
HD flexplate for high HP:
- SFI-rated for race use
- Required for some race classes
- Cost: $150-400
Cooling considerations
LS-swap typically benefits from external cooler:
- LS engines generate good heat for trans
- External cooler is highly recommended
- Especially in swaps where factory cooling was for original engine
Recommended cooler size for LS swap:
- 4L60E: 15,000-25,000 lb rated
- 4L80E: 20,000-35,000 lb rated
- 6L80: 20,000-30,000 lb rated
Driveline considerations
Driveshaft modifications:
- LS swap often changes trans length
- 4L60E vs 700R4 vs TH350 = different lengths
- Driveshaft must be matched
- Typical modification: $200-400
U-joint replacement:
- Cheap insurance during install
- $30-80 per U-joint
Crossmember:
- May need adapter or specific aftermarket crossmember
- Cost: $100-300 typical
Common LS swap transmission mistakes
Mistake 1: Wrong TCM
4L60E and 4L80E have different TCMs. 6L80 different again. Verify match.
Mistake 2: Skipping cooler
LS heat + stock cooler = trans failure. Always add external cooler.
Mistake 3: Wrong flexplate
LS has specific flexplate. Don't use random Chevy small block flexplate.
Mistake 4: Cheap rebuild
LS swap = significant investment. Don't cheap out on trans rebuild.
Mistake 5: Wrong torque converter
LS torque curve is different from older small blocks. Match converter to actual engine.
Mistake 6: Ignoring TV cable (if 700R4)
If using 700R4 behind LS: TV cable setup is critical. Many swap parts available.
Cost summary
Stock LS swap with rebuilt 4L60E:
- Rebuild kit: $400-700
- Adapter/mount: $100-300
- Wiring: $200-400
- Cooler: $100-200
- Driveshaft: $200-400
- Labor (if shop): $1,000-2,500
- Total: $2,000-4,500
Performance LS swap with built 4L80E:
- Build cost: $3,000-5,000
- Adapter/mount: $200-500
- Wiring: $300-500
- Cooler: $200-400
- Driveshaft: $300-500
- Labor: $1,500-3,000
- Total: $5,500-9,900
High-HP race LS swap with race 4L80E:
- Race build: $6,000-10,000
- Adapter/mount: $300-800
- Custom electronics: $500-1,000
- Race cooler: $300-600
- Race driveshaft: $400-800
- Labor: $3,000-5,000
- Total: $10,500-18,200
What we sell
LS swap rebuild kits for 4L60E and 4L80E, LS-specific flexplates, LS-pattern torque converters, swap mounting kits, TCM controllers, and complete LS swap transmission packages.
Doing an LS swap? Shop our LS swap catalog. 4L60E and 4L80E rebuild kits, LS flexplates, torque converters, TCM controllers, mounting kits. Free shipping over $70.
Related guides: