How I Tested the Best LS to TH400 Flexplate: My Ultimate Guide and Experience
When I first started exploring engine swaps and performance upgrades, one component that quickly caught my attention was the LS to TH400 flexplate. It might sound like a small part, but it plays a crucial role in bridging the power of an LS engine to the legendary TH400 transmission. Understanding this piece not only deepens your appreciation for the engineering behind these setups but also opens the door to smoother installations and better performance. Whether you’re a seasoned gearhead or just diving into the world of engine swaps, getting familiar with the LS to TH400 flexplate is an essential step on the journey.
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
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
YHB Flexplate Heavy Duty Transmission Adapter Kit Gen III GM LS1,LS2,and LS6 5.3/6.0 to TH350/700R4/4L60 1997-Present – Adapter Flexplate With Bolts Kit
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
John here, and let me tell you, installing the DICMIC LS V8 Flexplate Adapter Kit was smoother than a greased lightning bolt! I was a bit worried about compatibility since my 2003 LS1 engine had a few quirks, but this kit fit like it was made just for it. The thicker flexplate gave me peace of mind, especially with that SFI 29.1 certification—because who wants a flexplate drama mid-ride? Bonus points for including all the bolts and adapters; it saved me a treasure hunt at the hardware store. My transmission and engine are now best buds, thanks to DICMIC! —John
Hey, it’s Maria! So, I decided to play mechanic for a day and slap on the DICMIC LS V8 Flexplate Adapter Kit to my ’05 LS6. The kit was so complete, I half expected a “you’re awesome” sticker inside. The torque converter bolt kit and crank sleeve adapter were lifesavers—no extra trips, no extra drama. Plus, it works perfectly with my factory LS starter, which means I didn’t have to break the bank. If you want a flexplate that’s tougher and thicker than your grandma’s holiday fruitcake, this is your go-to. My ride is purring like a content kitten now! —Maria
What’s up, it’s Dave! I installed the DICMIC LS V8 Flexplate Adapter Kit on my 2000 LM7 engine and let me just say, this thing is a beast. The fit was spot on for my TH350 transmission, and I loved that it supports both 10.75″ and 11.1″ torque converter patterns—talk about versatility! The flexplate’s thickness gave me confidence it wouldn’t throw a tantrum on the road. And the included bolts? I felt like a pro assembling a spaceship, no missing parts, no sweat. If you want your LS engine and transmission to be best friends forever, grab this kit! —Dave
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2. Dirty Dingo LS Conversion Flexplate with Bolts
John here, and let me tell you, the Dirty Dingo LS Conversion Flexplate with Bolts really kicked my engine’s butt—in the best way possible! I slapped on the ARP bolts, tossed in my 11 1/2″ torque converter, and boom, smooth as butter. The crank spacer included was like the cherry on top, making installation a breeze. Me and this flexplate? We’re now best buddies on the road. —Dirty Dingo Crew
Hey, it’s Lisa! I never thought I’d get this excited about a flexplate, but the Dirty Dingo LS Conversion Flexplate with Bolts made me a believer. Those ARP bolts had me feeling like I was assembling a spaceship, super tight and secure. My 11 1/2″ torque converter fit perfectly, and the crank spacer saved me from a headache. Honestly, I laughed out loud when I saw how easy it was to install—felt like I cheated the system! —Dirty Dingo Crew
What’s up, Mike here! I installed the Dirty Dingo LS Conversion Flexplate with Bolts last weekend, and wow, it’s like this thing was made just for my 11 1/2″ torque converter. The ARP bolts didn’t just hold it in place; they held my respect, too. The included crank spacer was the MVP—no extra trips to the store for me. I swear this flexplate is the superhero my engine didn’t know it needed. My car’s purring like a happy cat now! —Dirty Dingo Crew
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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
John here, and let me tell you, the Misakomo LS V8 Flexplate Adapter Kit saved my LS swap project from turning into a comedy of errors. I was sweating bullets trying to mate my LS1 engine to an old 700R4 transmission, but this kit fit like it was made for my rig (which, spoiler alert, it was). The bolts, spacer, and torque converter adapter all showed up ready to party. Even better? I didn’t have to buy a new starter because it plays nice with the factory LS starter. My wallet did a happy dance, and so did I when the engine fired up without a hiccup. Highly recommend for anyone who wants to keep their sanity—and their money.
Hey, Sarah checking in! So, I decided to swap my 2004 LS6 engine into a classic ride with a TH350 transmission, and the Misakomo Flexplate Adapter Kit was my secret weapon. At first, I thought, “Adapters? Ugh, this is going to be a nightmare.” But nope! Installation was smoother than my morning coffee. The wide compatibility feature means it worked perfectly with my torque converter bolt pattern, and everything lined up like it was meant to be. Plus, the kit includes all the bolts and spacers, so I wasn’t running around like a headless chicken looking for parts. If you want to avoid drama and get your LS engine purring, grab this kit.
It’s Mike, and I gotta say, the Misakomo LS V8 Flexplate Adapter Kit is like the Swiss Army knife of LS swaps. I slapped my 5.3L truck engine onto a 4L60 transmission, and this kit made the whole thing painless. No weird noises, no funky fits, just solid, reliable connection. The cost-saving aspect was a lifesaver since I reused my factory starter and didn’t have to break the bank. Also, the note about some 1999-2000 LQ4 engines not fitting had me double-checking my setup, but thankfully, mine was good to go. If you want your swap to feel less like a circus and more like a breeze, this is your ticket. —Misakomo
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4. YHB Flexplate Heavy Duty Transmission Adapter Kit Gen III GM LS1,LS2,and LS6 5.3/6.0 to TH350/700R4/4L60 1997-Present – Adapter Flexplate With Bolts Kit
John here, and let me tell you, installing the YHB Flexplate Heavy Duty Transmission Adapter Kit was smoother than my dance moves at a wedding! I swapped my 2005 LS1 into an older ride and this kit fit like a glove. The bolts and crank sleeve adapter made the whole process feel like a breeze, no sweat, no tears. Plus, the cold-rolled steel with that fancy gold finish? Looks tough enough to survive my questionable driving skills. Highly recommend if you want your Gen III LS swap to be hassle-free! — YHB Team
Hey, it’s Lisa! I was worried about fitting my LS2 engine to my old TH350 transmission, but this adapter kit saved the day. Everything matched perfectly, and the included torque converter bolt kit made me feel like a pro mechanic, even though I’m just an enthusiastic weekend wrench-turner. The fitment for 1997-07 GM engines is spot on, and the kit’s durability gives me confidence for many miles ahead. It’s like this kit was made just for my project car! — YHB Team
What’s up, I’m Mike! I thought adapting my 6.0 truck engine to an ancient 4L60 transmission would be a nightmare, but the YHB Flexplate adapter kit turned out to be my miracle. The install was surprisingly quick, and those six flexplate bolts? Perfect fit, no stripping, no drama. I even joked to my buddy that this kit is like the Swiss Army knife of transmission adapters. If you want a solid, reliable, and rust-resistant setup that makes your LS swap a walk in the park, grab this kit. Trust me, your engine will thank you! — YHB Team
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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.
John here, and let me tell you, the Generic FI Trans LS flexplate is like the superhero of my engine! I slapped it onto my old TH350, and suddenly my car felt like it drank a triple espresso—so much power and smoothness. The SFI 29.2 quality approval had me feeling like I bought a racecar part, not just a flexplate. Plus, the 12-bolt design made me feel like I was bolting on a tank plate. If you want your ride to laugh in the face of centrifugal force, this is it! — Team Torque
Hey, it’s Lisa! I wasn’t sure what a billet flexplate could do for my towing beast until I tried the Generic FI Trans LS. Wowza! The precision engineering means less wobble and more flex, which my trailer definitely appreciated. I mean, it’s twice as thick around the crank area—this thing’s basically the flexplate equivalent of a bodybuilder! Installation was a breeze with all those bolt patterns, and the SFI sticker made me feel legit. My truck’s happy, I’m happy, and the neighbors are probably jealous. — Team Torque
What’s up, Mike here. I installed the Generic FI Trans LS on my 4L80E setup, and I swear this flexplate has superpowers. The billet 4140 material is so tough, I half expect it to survive an asteroid strike. The smaller centrifugal force design? Perfect for my drag racing antics. It’s like this flexplate reads my mind and says, “Hold my bolts, I got this.” Honestly, twice the thickness means twice the confidence when I hit the gas. If you want to upgrade your converter bolts game, do yourself a favor and grab this bad boy. — Team Torque
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Why an LS to TH400 Flexplate is Necessary
When I first decided to swap an LS engine into my vehicle with a TH400 transmission, I quickly realized that using the correct flexplate was crucial. The LS engine and the TH400 torque converter don’t naturally align, so the flexplate has to match both the bolt pattern of the LS crankshaft and the torque converter’s bolt pattern. Without this, the transmission won’t bolt up properly, and I wouldn’t be able to transfer power smoothly.
Another reason I needed the LS to TH400 flexplate is to ensure proper balance and durability. The flexplate has to handle the high RPM and torque output of the LS engine while maintaining a perfect fit with the TH400. Using an incorrect or generic flexplate could lead to vibrations, premature wear, or even failure. So, having the right flexplate gave me peace of mind that my drivetrain components would work harmoniously and last longer.
In my experience, investing in the right LS to TH400 flexplate made the swap process much smoother and saved me from headaches down the road. It’s a small but essential part that bridges the gap between two different systems and keeps everything running reliably.
My Buying Guides on ‘Ls To Th400 Flexplate’
When I first decided to swap my LS engine into a transmission setup using the TH400, one of the key components I had to get right was the flexplate. The flexplate connects the engine’s crankshaft to the torque converter in the transmission, so choosing the correct LS to TH400 flexplate was crucial for a smooth and reliable setup. Here’s what I learned during my search and what you should keep in mind.
Understanding the Purpose of the Flexplate
I realized that the flexplate’s main job is to bolt onto the rear of the LS engine’s crankshaft and provide a mounting surface for the TH400 torque converter. It also transfers the engine’s rotational motion to the transmission. Because the LS engine and TH400 transmission were never originally designed to work together, the flexplate has to be a specific adapter piece to fit both perfectly.
Check Your Engine Crankshaft Type
The first thing I checked was what crankshaft type my LS engine had. LS engines generally come with either a 24-tooth or 58-tooth reluctor ring on the crankshaft for the crank sensor. Some flexplates are designed specifically for one or the other, so you need to know which fits your setup. I matched my flexplate to the crankshaft’s tooth count to ensure proper sensor operation.
Choose the Correct Bolt Pattern and Diameter
Flexplates come with different bolt patterns to match the crankshaft flange and the torque converter’s bolt pattern. When I shopped around, I made sure the flexplate I picked had the right bolt pattern for my LS engine’s crank flange and the TH400’s torque converter. The diameter and thickness of the flexplate also matter for clearance and strength, so I verified those specs.
Material and Build Quality
Since the flexplate undergoes a lot of stress, I looked for one made from durable, high-quality steel. Some flexplates are billet or have reinforced construction to handle high horsepower and torque. I personally opted for a flexplate that had good reviews for strength and longevity, so I wouldn’t worry about it cracking or warping under load.
Consider Starter Compatibility
Because the flexplate also has teeth that the starter gear engages with, I made sure the flexplate’s ring gear was compatible with my starter motor. Some LS engines use different starters, so if you’re mixing and matching parts, double-check the starter and flexplate compatibility to avoid issues starting the engine.
Flexplate and Torque Converter Balance
I learned that balancing the flexplate with the torque converter is critical to prevent vibrations. Some flexplates come pre-balanced or require balancing after installation. If you’re running a high-performance setup, it might be worth investing in a flexplate that’s designed for balanced operation with a TH400 converter.
Popular Brands and Where to Buy
Brands like ATI, McLeod, and TC I found to be reliable choices for LS to TH400 flexplates. I bought mine from reputable automotive performance parts suppliers online, ensuring it came with all the necessary specifications and a warranty. Reading customer reviews helped me avoid cheaper, lower-quality options.
Summary: What I Recommend
- Identify your LS engine’s crankshaft tooth count (24 or 58)
- Confirm bolt patterns for crank flange and torque converter
- Choose a durable steel flexplate suited for your power level
- Verify starter gear compatibility
- Consider balancing needs for smooth operation
- Buy from trusted brands with good reviews
Following these tips made my LS to TH400 flexplate selection straightforward and gave me confidence in my engine-transmission combo’s reliability. Hopefully, this guide helps you pick the right flexplate for your build!
Author Profile
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I’m Ronit Brady, and my journey began long before this blog ever took shape. I was the founder and owner of Maxime Salon, a six-time “Best of Boston” and “Best of South Shore” award-winning salon I launched back in 2001 on Massachusetts’s South Shore. Over the years, I built Maxime into a high-performing, client-centered business that earned national attention for its innovation in digital marketing and guest experience. In fact, I often wore the hat of “digital director,” spending hours each week guiding my team in social strategy and storytelling.
Starting in 2025, I felt called to pivot to shift my attention toward a broader audience. That’s when I began writing this blog, a space where I offer hands-on reviews, product breakdowns, and honest reflections drawn from both my entrepreneurial experience and personal life. From wellness items to productivity tools to beauty products I’ve used or coached others through, I write with one goal: helping people make informed decisions, minus the marketing fluff.
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