LS to TH400 Flexplate Kit (Gen III / LS Engines)
This Advance Adapters LS to TH400 flexplate kit is designed to properly mate Gen III / LS-series engines to GM TH400 automatic transmissions. It provides the correct spacing and bolt pattern needed to ensure reliable torque converter engagement and smooth drivetrain operation.
The kit includes a custom LS flexplate, 11mm flexplate bolts, and a crank spacer, making it a complete solution for adapting an LS engine to a TH400 transmission.
Designed for Gen III / LS Engines
Gen III / LS-series engines (4.8L, 5.3L, 5.7L LS1, 6.0L, and 6.2L) feature a crankshaft that sits approximately 0.400 inches closer to the block than traditional small-block Chevy engines. In addition, the LS crankshaft uses a unique bolt pattern that requires an LS-specific flexplate.
This LS flexplate is dished to compensate for the recessed crankshaft, positioning the flexplate correctly in relation to the transmission while maintaining proper torque converter spacing. The included crank spacer accounts for the shorter crank stick-out, allowing the TH400 torque converter to seat correctly.
How This Kit Adapts an LS to a TH400
Advance Adapters solves the LS-to-TH400 compatibility issue by combining:
- A custom LS flexplate drilled for TH400 torque converters
- A precision crank spacer to correct crankshaft depth
- Proper 11mm flexplate bolts for secure installation
Together, these components allow a TH400 transmission to bolt up correctly to an LS engine without driveline misalignment or converter engagement issues.
Compatibility Notes (Important)
- Designed for Gen III / LS engines only
Not compatible with:
LS7, LS9, LSA, or LSX engines (8-bolt crank)
2014+ Gen V LT engines (LT1, 4.3L V6, 5.3L, 6.2L)
Some 6.0L engines with cast-iron cylinder heads use a different crankshaft stick-out and should retain their original transmission
Certain 1999–2003 4.8L engines originally paired with manual transmissions may not have a recessed crank and are not compatible
Always verify engine crankshaft configuration before ordering.
Kit Includes (Bill of Materials)
- Flexplate – GM LS Engine to TH400/TH350 (711500A4)
- Gen III LS 11mm Flexplate Bolt Set (716141A)
- Gen III Crank Spacer / Bushing (716155A)
Bill Of Materials
