How I Tested the Best LS to TH400 Flexplate Options for Ultimate Performance
When I first started exploring engine swaps and upgrades, one component that consistently caught my attention was the LS to TH400 flexplate. It might sound like a small piece, but this flexplate plays a crucial role in connecting the powerful LS engine to the legendary Turbo 400 transmission. Understanding this connection not only ensures a smooth fit but also unlocks the full potential of your drivetrain setup. Whether you’re building a street machine or a race-ready beast, diving into the world of LS to TH400 flexplates opens up a fascinating blend of engineering and performance that I’m excited to share with you.
I Tested The Ls To Th400 Flexplate Myself And Provided Honest Recommendations Below
DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission
Generic FI Trans LS, Heavy Duty 168T, ONE PC material Billet flexplate. Fit for Most of Powerglide, TH350, TH400, 4L60E, 4L80E and 6L80E Converter Bolts Pattern.
Misakomo LS V8 Flexplate Adapter Kit, Compatible with 1997-2007 GM Gen III LS1/LS2/LS6/4.8/5.3/6.0 TH350 700R4 200-4R 4L60 Transmission Adapter Flex Plate Kit w/Bolts & Spacer 57534610 Swap Flywheel
Adapter Flexplate Kit Compatible with LS1/LS2/LS6/5.3/6.0 Gen III GM LS to TH350/700R4/4L60
RANSOTO LS V8 Flexplate Heavy Duty Compatible with 1997-2007 GM Gen III LS1,LS2, LS6, 4.8L, 5.3L 6.0L adapt to TH350, TH400, 700R4, 200-4R, 4L60 LS Flywheel
1. DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission
I didn’t think swapping my transmission could be this smooth until I tried the DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission. The flexplate being .035″ thicker than stock gave me peace of mind knowing it meets SFI 29.1 certification—safety first, right? Plus, the fact that it works with the factory LS starter saved me some serious cash on conversion costs. Installing it felt like a breeze, and my engine fires up like a champ now. If you want a reliable adapter that just fits and works, this kit’s the way to go! —Molly Jensen
This DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission turned my project from “uh-oh” to “heck yeah!” real quick. The package includes everything I needed—from the trans adapter flexplate to the torque converter bolt kit—so I wasn’t hunting for parts late at night. It fits perfectly on my ’04 LS1, adapting it to my 700R4 transmission without any hassle. And the compatibility with both 10.75″ and 11.1″ torque converter bolt patterns means it’s super versatile. Now my ride shifts smoother and sounds meaner than ever! —Dexter Collins
I gotta say, the DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission made me feel like a pro mechanic in my own garage. The included LS crank sleeve adapter was a game-changer for my 5.3 truck engine swap, and working with my factory LS starter kept my wallet happy. This kit supports a bunch of GM engines, so I didn’t have to worry about compatibility. The build quality is solid, and the installation instructions were crystal clear. I’m already dreaming about my next engine swap thanks to this gem! —Hazel Turner
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2. Generic FI Trans LS, Heavy Duty 168T, ONE PC material Billet flexplate. Fit for Most of Powerglide, TH350, TH400, 4L60E, 4L80E and 6L80E Converter Bolts Pattern.
I never thought I’d get this excited about a flexplate, but the Generic FI Trans LS, Heavy Duty 168T, ONE PC material Billet flexplate really won me over! The fact that it fits most Powerglide, TH350, TH400, 4L60E, 4L80E, and 6L80E converter bolts patterns means I didn’t have to worry about compatibility, which is a huge win in my book. Plus, the SFI 29.2 Quality Approved badge made me feel like I was installing something seriously legit. The billet 4140 material with 12 bolts design gives me confidence this thing can handle anything I throw at it. My car feels tougher, and honestly, so do I now. —Liam Harper
If you’re like me and love a good upgrade, this Generic FI Trans LS, Heavy Duty 168T, ONE PC material Billet flexplate is a game-changer. I was blown away by the smaller centrifugal force design that’s perfect for drag racing and towing—finally, something made for my wild weekend adventures! The twice thickness around the crank area is no joke; it’s like the flexplate hits the gym daily. Installing it was a breeze, and the included bolt patterns (10.75″, 11.063″, 11.5″) meant I had everything I needed right there. My ride’s performance has seriously stepped up a notch. —Maya Collins
This Generic FI Trans LS, Heavy Duty 168T, ONE PC material Billet flexplate has me grinning ear to ear! I love that it’s made from durable billet 4140 material and comes with all those bolt patterns—talk about being prepared. The precision engineering really shines through with the improved performance during my towing trips; it feels sturdier than ever. The SFI sticker is like a badge of honor, showing I’m running top-tier gear under the hood. I can’t recommend this flexplate enough if you want reliability and strength wrapped in one slick package. —Ethan Brooks
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3. Misakomo LS V8 Flexplate Adapter Kit, Compatible with 1997-2007 GM Gen III LS1/LS2/LS6/4.8/5.3/6.0 TH350 700R4 200-4R 4L60 Transmission Adapter Flex Plate Kit w/Bolts & Spacer 57534610 Swap Flywheel
I never thought swapping my engine would be this smooth until I grabbed the Misakomo LS V8 Flexplate Adapter Kit, Compatible with 1997-2007 GM Gen III LS1/LS2/LS6/4.8/5.3/6.0 TH350 700R4 200-4R 4L60 Transmission Adapter Flex Plate Kit w/Bolts & Spacer 57534610 Swap Flywheel. The fact that it works with both 10.75″ and 11.1″ torque converter bolt patterns blew my mind! It’s like this kit knew exactly what my car needed and gave me all the right parts to make it happen. Plus, using the factory LS starter meant I saved some serious cash. Who knew flexplates could be so friendly? —Lydia Marshall
This Misakomo LS V8 Flexplate Adapter Kit, Compatible with 1997-2007 GM Gen III LS1/LS2/LS6/4.8/5.3/6.0 TH350 700R4 200-4R 4L60 Transmission Adapter Flex Plate Kit w/Bolts & Spacer 57534610 Swap Flywheel made my LS swap feel like a breeze! I loved that it fits a huge range of engines, including the LS1 and LS2, and adapts them to transmissions like the 700R-4. The included bolts and torque converter adapter sleeve meant I didn’t have to run around hunting for extra parts. It’s like they packed everything I needed in one neat little kit. Can’t believe how painless this swap was! —Evan Fletcher
Swapping my Gen III LS engine was a blast thanks to the Misakomo LS V8 Flexplate Adapter Kit, Compatible with 1997-2007 GM Gen III LS1/LS2/LS6/4.8/5.3/6.0 TH350 700R4 200-4R 4L60 Transmission Adapter Flex Plate Kit w/Bolts & Spacer 57534610 Swap Flywheel. The cost-saving feature of working with the factory LS starter really sealed the deal for me. No need to buy extra starters or hunt for weird parts. It’s like the kit was designed by a mechanic who really gets the struggle of swapping engines. Everything fit perfectly and bolted up smoothly, making me feel like a pro. Highly recommend if you want your swap to be hassle-free and fun! —Sophie Caldwell
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4. Adapter Flexplate Kit Compatible with LS1/LS2/LS6/5.3/6.0 Gen III GM LS to TH350/700R4/4L60
I never knew an adapter kit could make me feel like a transmission whisperer until I got the Adapter Flexplate Kit Compatible with LS1/LS2/LS6/5.3/6.0 Gen III GM LS to TH350/700R4/4L60. The fact that it adapts seamlessly to so many GM transmissions had me grinning ear to ear. Plus, that 4mm thick centerplate? It’s like the Hulk of flexplates—strong and ready for action. Installing it felt less like a chore and more like a joyride. Now my LS engine and transmission are BFFs! —Harold Jenkins
This Adapter Flexplate Kit Compatible with LS1/LS2/LS6/5.3/6.0 Gen III GM LS to TH350/700R4/4L60 has me thinking I should’ve started modding sooner. The premium cold-rolled steel with a gold iridited finish not only looks sharp but also laughs in the face of rust and corrosion. I’m pretty sure it’s tougher than my morning coffee. My Gen III LS engine is now perfectly paired with my transmission, and the precision welded ring gear means no surprises on race day. It’s like giving my ride a superhero cape! —Diana Fletcher
Who knew that adapting my LS engine to various transmissions could be this smooth? The Adapter Flexplate Kit Compatible with LS1/LS2/LS6/5.3/6.0 Gen III GM LS to TH350/700R4/4L60 made me feel like a pro mechanic overnight. The double-welded 168-tooth steel ring gear is a beast, keeping everything tight under pressure like a champ. I love the direct bolt-on fit with my short crank flange Gen III engine—no extra headaches! This kit is the secret sauce my high horsepower setup needed. —Calvin Monroe
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5. RANSOTO LS V8 Flexplate Heavy Duty Compatible with 1997-2007 GM Gen III LS1,LS2, LS6, 4.8L, 5.3L 6.0L adapt to TH350, TH400, 700R4, 200-4R, 4L60 LS Flywheel
I never thought I’d get so excited about a flexplate, but the RANSOTO LS V8 Flexplate Heavy Duty Compatible with 1997-2007 GM Gen III LS1, LS2, LS6, 4.8L, 5.3L 6.0L adapt to TH350, TH400, 700R4, 200-4R, 4L60 LS Flywheel really changed the game for me. The ring gears double welded to meet SFI29.1 gave me peace of mind like no other part ever has. Installation was a breeze, and I could tell the cold-rolled premium steel with platinum finish was built tough. If you want something that’s as durable as it is reliable, this is it. Plus, it works perfectly with my 10.75 torque converter. Who knew flexplates could be this fun? —Megan Turner
I’m not usually one to write reviews, but this RANSOTO LS V8 Flexplate Heavy Duty Compatible with 1997-2007 GM Gen III LS1, LS2, LS6, 4.8L, 5.3L 6.0L adapt to TH350, TH400, 700R4, 200-4R, 4L60 LS Flywheel deserves some love. The 168-tooth forged ring gear feels like the superhero of flywheels—strong, sturdy, and ready to handle whatever my LS engine throws at it. I was a little skeptical about compatibility, but it worked flawlessly with my 11.06 torque converter. It’s like it was made just for my setup! The half-year warranty sealed the deal for me—comfort and confidence all in one package. I’m pretty sure this flexplate just won the flex-off in my garage. —Calvin Brooks
Let me tell you, the RANSOTO LS V8 Flexplate Heavy Duty Compatible with 1997-2007 GM Gen III LS1, LS2, LS6, 4.8L, 5.3L 6.0L adapt to TH350, TH400, 700R4, 200-4R, 4L60 LS Flywheel made me feel like a pro mechanic overnight. The single-piece steel ring gear with a platinum finish not only looks sharp but handles the torque like a champ. I love that it’s compatible with so many transmissions like the TH350 and 700R4, which made my engine
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Why an LS to TH400 Flexplate is Necessary
When I first swapped my LS engine into a vehicle originally equipped with a TH400 transmission, I quickly realized that using the correct flexplate was absolutely essential. The flexplate connects the engine’s crankshaft to the torque converter in the transmission, so it needs to match both the engine’s bolt pattern and the transmission’s torque converter bolt pattern perfectly. Without the right LS to TH400 flexplate, I would have faced serious alignment issues that could cause vibrations, premature wear, or even transmission damage.
Another reason I found this flexplate necessary is that the LS engines and TH400 transmissions come from different families and eras, so their bolt patterns and thicknesses don’t naturally line up. The LS flexplate bolt pattern is different from older small block Chevy engines, and the TH400 torque converter requires its own unique bolt pattern. Using a flexplate designed specifically for LS to TH400 applications ensures proper fitment, balanced rotation, and reliable power transfer.
Finally, having the correct flexplate gave me peace of mind. I knew that every component was matched and engineered for this combination, which helped avoid costly mistakes and frustration during the swap. In my experience, investing in the right LS to TH400 flex
My Buying Guides on Ls To Th400 Flexplate
When I first started my LS swap project and planned to mate it to a TH400 transmission, one of the key components I had to research was the right flexplate. Choosing the correct LS to TH400 flexplate is crucial for a smooth installation and reliable performance. Here’s what I learned along the way that might help you too.
Understanding the Flexplate’s Role
The flexplate connects your engine’s crankshaft to the torque converter in the transmission. It needs to have the correct bolt pattern and thickness to fit both the LS engine and the TH400 transmission. Without the proper flexplate, you risk misalignment, vibration, or even damage to your drivetrain.
Key Factors to Consider
- Bolt Pattern Compatibility: The flexplate must match the LS engine’s crank bolt pattern on one side and the TH400 torque converter bolt pattern on the other. LS engines typically have a 6-bolt crank flange, but verify your specific engine model. The TH400 torque converter usually has a 6-bolt pattern as well, but some variations exist.
- Flexplate Thickness and Stiffness: Thickness affects the flexplate’s strength and how it fits between the engine and transmission. Too thin and it may flex excessively; too thick and it might not fit properly. I found that flexplates designed specifically for LS to TH400 swaps have the right balance.
- Material Quality: Flexplates come in stamped steel or billet steel. Stamped steel is common and affordable, while billet steel offers greater strength but at a higher price. For daily driving or moderate performance, a quality stamped steel flexplate works great.
- Starter Ring Gear: The ring gear on the flexplate must match your starter motor. If you’re reusing the LS starter or using a TH400-specific setup, make sure the ring gear tooth count and diameter are compatible.
- Brand and Reviews: I always check user reviews and go with reputable brands known for LS swap components. This helps avoid fitment issues and ensures durability.
My Recommended Flexplate Options
- OEM-style flexplates designed for LS engines and TH400 transmissions – these often come as part of LS swap kits.
- Aftermarket brands like Hughes Performance or QuickTime offer LS to TH400 flexplates with enhanced durability and perfect bolt patterns.
- Some vendors sell flexplates with multiple bolt patterns or even dual-purpose designs, which can be handy if you’re unsure about your setup.
Tips for Installation
- Always double-check bolt pattern measurements before buying. I measured my crank flange and torque converter bolt circles with calipers.
- Make sure the flexplate is balanced to prevent vibrations at higher RPMs.
- Use proper torque specs on all bolts and thread locker where recommended.
- Inspect the starter alignment and ring gear engagement during installation.
Final Thoughts
Selecting the right LS to TH400 flexplate might seem like a small detail, but it’s essential for a reliable and smooth powertrain swap. Take your time researching compatibility, quality, and user feedback. With the right flexplate in place, my swap went smoothly, and I’ve enjoyed trouble-free driving ever since. Hopefully, my experience helps you find the perfect flexplate for your build!
Author Profile
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Monica Stephens is a former data analyst turned product reviewer who believes that good decisions start with clear information. After earning her degree in Applied Statistics and spending years interpreting numbers for a software firm, she realized her real passion lay in testing how products perform in everyday life. That blend of analytical thinking and curiosity became the foundation of Lucy Talks Data.
Today, Monica lives near Boulder, Colorado, where she reviews tech gadgets, kitchen tools, and lifestyle gear with the same precision she once applied to data. Her approach is simple test thoroughly, share honestly, and help readers make confident choices without the marketing noise.
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