LS Flexplate Adapter Spacer | TH350 TH400 LS1 LS2 LS3 Swap
LS Flexplate Adapter Spacer | TH350 TH400 LS1 LS2 LS3 Swap
LS Flexplate Adapter Spacer — TH350 & TH400 Transmission Conversion
Tackle your LS engine swap with confidence using this precision-machined Flexplate Adapter Spacer. Engineered for 1998–2004 LS1-based engines, this adapter is the key component you need when mating a TH350 or TH400 transmission to an LS1, LS2, LS3, or LSX engine using a curved (dished) flexplate. A must-have for any classic muscle car or truck build going through an LS conversion.
Why You Need This Adapter Spacer
When swapping an LS engine into an older vehicle using a TH350 or TH400 automatic transmission, the bolt pattern and flexplate geometry require a proper adapter spacer to ensure correct alignment and torque converter engagement. This spacer bridges the gap cleanly, giving you a solid, rattle-free connection between your LS engine and your chosen transmission.
Key Features
- Compatible Engines: 1998–2004 LS1-based engines (LS1, LS2, LS3, LSX)
- Compatible Transmissions: TH350, TH400
- Material: Durable steel construction for long-lasting performance
- Dimensions: Approx. 50 x 26 mm (1.97 x 1.02 in)
- Designed for use with a curved/dished flexplate
- Straightforward fitment — ideal for experienced builders and seasoned DIYers alike
What's in the Box
- 1 × LS Flexplate Adapter Spacer
Specifications
| Material | Steel |
| Dimensions | Approx. 50 x 26 mm / 1.97 x 1.02 in |
| Engine Fitment | LS1, LS2, LS3, LSX (1998–2004) |
| Transmission Fitment | TH350, TH400 |
| Flexplate Type Required | Curved/Dished Flexplate |
Safe & Reliable Engine Swap Advice
Always follow proper torque specifications and consult your vehicle's service manual during any drivetrain conversion. For general automotive safety guidance, visit the U.S. Consumer Product Safety Commission (CPSC).
Learn more: Automatic transmission
Frequently Asked Questions
Q: What engines and transmissions is this flexplate adapter spacer compatible with?
A: This adapter spacer is designed for use with 1998–2004 LS1-based engines — including LS1, LS2, LS3, and LSX — paired with a TH350 or TH400 automatic transmission. It is specifically intended for builds using a curved (dished) flexplate.
Q: What material is this adapter spacer made from, and what are the dimensions?
A: The flexplate adapter spacer is constructed from durable steel, measuring approximately 50 x 26 mm (1.97 x 1.02 in), making it compact yet robust enough for the demands of a drivetrain conversion swap.
Q: Do I need any special tools to install the LS TH350/TH400 flexplate adapter spacer?
A: Installation typically requires standard automotive hand tools and should be performed by someone familiar with LS engine swaps and automatic transmission fitment. Always reference your specific vehicle and transmission service documentation for correct torque values and procedures.
Q: Is this suitable for a TH350 swap as well as a TH400 swap?
A: Yes — this adapter spacer works with both the TH350 and TH400 transmissions when converting to an LS engine platform using a curved flexplate, making it a versatile solution for a variety of classic GM vehicle builds.