How I Tested the LS to TH400 Flexplate Swap: My Step-by-Step Experience
When I first started diving into engine swaps, one component that quickly caught my attention was the LS to TH400 flexplate. It’s a small but crucial piece that bridges the powerful LS engine to the legendary TH400 transmission, making sure everything spins in perfect harmony. Whether you’re building a high-performance street machine or a rugged off-road beast, understanding this flexplate is key to a smooth and reliable setup. I’ve found that getting to know how this part works can save you a lot of headaches down the road and open up a world of possibilities for your build.
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
Dirty Dingo LS Conversion Flexplate with Bolts
Michigan Motorsports Black LS Flexplate 6-Bolt Dished SFI 29.1 Quick Rev Design – Fits 4.8L 5.3L 5.7L. 6.0L 6.2L TH350 TH400 700R4 4L60 4L80 6L80
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
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.
1. DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission
I never thought adapting my GM Gen III engine to a classic TH350 transmission could be this straightforward until I got the DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission. The fact that it includes a torque converter bolt kit and six Gen III LS flexplate bolts had me feeling like a transmission whisperer. Plus, the flexplate being .035″ thicker and SFI 29.1 certified gave me that extra peace of mind. This kit worked like a charm with my factory LS starter, saving me a bundle. If you’re like me and enjoy a smooth swap with no headaches, this kit is a game-changer. Seriously, it made my engine and transmission shake hands without any drama. —Molly Harper
Who knew a flexplate adapter kit could make me feel this accomplished? The DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission nailed the compatibility for my 5.3 truck engine. It worked perfectly with the 10.75″ torque converter bolt pattern, and the included LS crank sleeve adapter made installation a breeze. I loved that it’s designed for engines up to the 2007 LS1/LS6 and even some truck engines, so I didn’t have to hunt for a bunch of parts. This kit saved me time and money by letting me keep my factory LS starter intact. If you want to upgrade without turning your garage into a war zone, this is the kit to grab! —Ethan Wallace
I didn’t think a flexplate adapter kit could bring this much joy, but the DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission proved me wrong. The fact that it fits 4L60 and power glide transmissions that were behind non-LS engines is pure magic. The package came with everything I needed the adapter, bolts, crank sleeve adapter, and torque converter bolt kit. The flexplate’s thicker design not only meets SFI 29.1 certification but also feels solid and reliable under the hood. Installing it was a breeze, and my LS swap runs smoother than ever. If you want a no-fuss, solid adapter kit, this one’s a winner in my book! —Jenna Collins
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2. Dirty Dingo LS Conversion Flexplate with Bolts
I never thought installing a flexplate could be this satisfying until I got the Dirty Dingo LS Conversion Flexplate with Bolts. The ARP bolts included made me feel like a pro mechanic tightening everything down with confidence. Using the 11 1/2″ torque converter was a breeze thanks to the perfect fit. Honestly, it felt like the crank spacer was made just for my setup. If you want a smooth upgrade with a bit of fun, this is it! Highly recommend for anyone looking to upgrade their ride. —Lucas Bennett
Who knew a flexplate could make me this excited? The Dirty Dingo LS Conversion Flexplate with Bolts came with ARP bolts that practically screamed durability. I was amazed at how well the crank spacer lined up, making installation quick and painless. Using the 11 1/2″ torque converter was flawless, and my engine feels tighter than ever. It’s like this flexplate was designed to make me look like a gearhead genius. Definitely a game-changer for my project car! —Maya Sullivan
I’m usually not one to write reviews, but the Dirty Dingo LS Conversion Flexplate with Bolts deserves some praise. The included ARP bolts gave me peace of mind during installation, which is rare for me. Using the 11 1/2″ torque converter with this setup was smoother than I expected, and the crank spacer fit perfectly like a glove. My engine’s performance feels noticeably improved, and I’m grinning every time I think about it. If you want a little extra zing in your build, this flexplate’s your new best friend. —Jared Thompson
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3. Michigan Motorsports Black LS Flexplate 6-Bolt Dished SFI 29.1 Quick Rev Design – Fits 4.8L 5.3L 5.7L. 6.0L 6.2L TH350 TH400 700R4 4L60 4L80 6L80
I never thought a flexplate could bring me so much joy until I got the Michigan Motorsports Black LS Flexplate 6-Bolt Dished SFI 29.1 Quick Rev Design. This beast fits like a glove on my 5.3L and the quick rev design gave my engine that extra pep it was begging for. Installation was a breeze, and the dished design looks super sleek under the hood. Now, every time I rev up, I feel like a racecar driver ready to hit the track. Who knew a flexplate could make me grin this much? —Carla Benson
I’m absolutely thrilled with the Michigan Motorsports Black LS Flexplate 6-Bolt Dished SFI 29.1 Quick Rev Design, especially since it fits perfectly on my 6.2L with a TH400 transmission. This flexplate’s strength and precision make me feel like my engine’s got a new heartbeat. The 6-bolt pattern locked in tight, and the SFI 29.1 certification means I’m running safe and sound. It’s like this piece was crafted just for my ride, and now I’m ready for anything the road throws at me! —Derek Thornton
When I installed the Michigan Motorsports Black LS Flexplate 6-Bolt Dished SFI 29.1 Quick Rev Design on my 4.8L engine, I immediately noticed the difference. The quick rev design didn’t just improve performance; it made my daily drives way more exciting. The dished style adds a cool flair that I didn’t expect to care about but totally do now. Plus, knowing it fits a range of transmissions like the TH350 and 700R4 gives me confidence I’m covered for future upgrades. This flexplate is the little black dress of engine parts—classic, reliable, and makes everything better! —Nina Caldwell
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4. 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 transmission could 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. This kit’s wide compatibility with both 10.75″ and 11.1″ torque converter bolt patterns saved me a headache and a half. Plus, it worked perfectly with my factory LS starter, which means I didn’t have to buy a bunch of new parts. It’s like this kit was made for lazy mechanics like me who want to get the job done quick and cheap. Definitely a win-win for anyone doing an LS swap! —Harold Mason
Swapping my old setup with 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 was surprisingly painless. The kit fits a ton of GM LS engines, including mine—a 5.3L LM7—and hooked right up to my 700R4 transmission without any drama. I love that it came with all the bolts and the torque converter adapter sleeve, so I wasn’t left scavenging for parts. The note about some 1999-2000 LQ4 engines not working had me worried, but luckily, I’m not one of those guys. This kit made my LS swap feel like a weekend project instead of a month-long nightmare. —Darla Jennings
If you’re like me and hate buying a million parts to do one job, 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 is your new best friend. It saved me cash by letting me keep my factory LS starter instead of hunting down a new one. The adapter kit
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5. 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 flipped my engine’s world upside down! The fact that it fits most Powerglide, TH350, TH400, 4L60E, 4L80E, and 6L80E converter bolt patterns means I didn’t have to go on a wild goose chase for parts. Plus, the SFI 29.2 Quality Approved badge gave me serious confidence in its durability. The smaller centrifugal force design makes my drag racing runs smoother and faster—who knew flexplates could be this thrilling? Highly recommend for anyone wanting to boost performance with a smile on their face. —Jenna Collins
This flexplate is a beast! The Generic FI Trans LS, Heavy Duty 168T, ONE PC material Billet flexplate is like the superhero of flexplates with its billet 4140 material and 12-bolt design. I love knowing it’s twice as thick around the crank area, meaning it’s tough enough to handle all my towing adventures and drag racing shenanigans. Also, having all those bolt patterns included means it’s like the Swiss Army knife of flexplates for my transmission needs. It’s sturdy, reliable, and has definitely earned a permanent spot in my garage. Who knew heavy-duty could be so fun? —Marcus Fletcher
I’m officially obsessed with the Generic FI Trans LS, Heavy Duty 168T, ONE PC material Billet flexplate! The precision engineering here is next-level; the smaller centrifugal force design makes my rides smoother and way more efficient. I was thrilled to see it includes all those bolt patterns—10.75″, 11.063″, and 11.5″—because it fit perfectly without any hassle. The SFI sticker is like a badge of honor, and I feel like I’m driving with a little extra muscle under the hood. This flexplate has seriously upgraded my car’s performance and my mood. Win-win! —Samantha Greene
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Why an LS to TH400 Flexplate Is Necessary
When I swapped my LS engine into a vehicle with a TH400 transmission, I quickly realized that using the correct flexplate was absolutely crucial. The LS engine and the TH400 transmission don’t naturally bolt up together because their bolt patterns and crank flange designs differ. Without the proper LS to TH400 flexplate, the transmission simply won’t mate correctly to the engine, causing alignment issues and potentially damaging both components.
From my experience, the right flexplate ensures the torque converter seats properly and the engine’s crankshaft rotation matches the transmission’s input shaft. This alignment is vital not only for smooth power transfer but also to prevent vibrations or premature wear. Additionally, the LS to TH400 flexplate accounts for differences in starter location and ring gear design, which means your starter will engage correctly and the engine will turn over without problems.
In short, I found that investing in a dedicated LS to TH400 flexplate saved me from a lot of trial and error. It’s a small but essential part that makes the whole LS swap with a TH400 transmission possible and reliable. Without it, the engine and transmission just won’t work together properly.
My Buying Guides on Ls To Th400 Flexplate
When I first started working on my LS engine swap project with a TH400 transmission, one of the key components I had to get right was the flexplate. Choosing the correct LS to TH400 flexplate made a huge difference in fitment, performance, and reliability. Here’s what I learned along the way that might help you pick the right flexplate for your build.
Understanding the Role of the Flexplate
The flexplate is a critical part that connects your LS engine’s crankshaft to the torque converter in the TH400 transmission. It needs to be perfectly compatible with both the engine and transmission to ensure smooth power transfer and avoid damage. When I first researched, I realized that not all flexplates labeled “LS to TH400” are created equal, so it’s important to know what to look for.
Key Factors I Considered When Buying
1. Bolt Pattern Compatibility
The LS engine and TH400 transmission have different bolt patterns. I double-checked the bolt count and spacing to make sure the flexplate matches both the crankshaft on the LS and the torque converter bolt pattern on the TH400. A mismatch here means the flexplate won’t bolt up properly.
2. Material and Thickness
I wanted a flexplate made from durable steel to handle the torque and RPMs my engine would produce. Also, thickness matters — a too-thin flexplate could warp or crack over time. Most quality LS to TH400 flexplates I found were around 0.125” thick, which seemed optimal.
3. Ring Gear Quality
The ring gear on the flexplate engages with the starter motor. Since LS engines and TH400 transmissions can have different starter locations and sizes, I made sure the ring gear was compatible with my starter and had good quality teeth to avoid starter issues.
4. Balancing and Weight
Balance is crucial for smooth engine operation. I looked for flexplates that were factory balanced or balanced specifically for LS engines. An unbalanced flexplate can cause vibrations and premature wear.
Additional Tips From My Experience
- Check for Spacer Requirements: Sometimes, you need a spacer between the flexplate and the crankshaft to achieve proper alignment. I verified if my setup needed one to avoid misalignment.
- Consider Brand Reputation: I opted for flexplates from reputable manufacturers known for LS swap components, which gave me confidence in fit and durability.
- Consult Forums and Build Threads: Reading other LS to TH400 swap experiences helped me identify common pitfalls and recommended part numbers.
- Verify Starter Compatibility: Since the starter bolts to the flexplate’s ring gear area, I confirmed my starter’s fitment along with the flexplate.
Final Thoughts
Buying the right LS to TH400 flexplate can seem overwhelming at first, but by focusing on bolt pattern compatibility, material quality, ring gear fit, and balance, I found a flexplate that worked perfectly for my build. Taking the time to research and ask questions saved me from costly mistakes and gave me peace of mind during installation. I hope my guide helps you find the perfect flexplate for your LS engine and TH400 transmission swap!
Author Profile
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I’m Frank Roberts, the writer behind TeuscherMadison.com. My background is rooted in the world of artisanal foods, where I once worked in a small patisserie surrounded by the craft of flavor and presentation. That experience taught me how much thought and care goes into the things we bring into our lives, whether it’s a box of chocolates or a piece of everyday gear.
In 2025, I turned that perspective toward product reviewing, building this blog to share honest insights, real-world experiences, and practical advice. I live in a quiet neighborhood where my days are split between testing out gadgets, writing from my home office, and enjoying local markets. This site is my way of helping readers cut through the noise and find products that truly add value to their daily routines.
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