How I Tested the Best LS to TH400 Flexplate Options for a Perfect Fit
When I first started diving into engine swaps and performance upgrades, one component that consistently caught my attention was the LS to TH400 flexplate. It’s one of those crucial yet often overlooked parts that can make or break the connection between your powerful LS engine and the trusty TH400 transmission. Understanding how this flexplate works and why it’s so important opened up a whole new level of appreciation for the engineering behind these setups. Whether you’re building a street machine or a full-on race car, getting this piece right is essential to ensuring everything spins smoothly and reliably under the hood.
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
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
Flexplate Adapter Kit with Converter Adapter Kit for TH350 TH400 TH700R4 Transmission for Impala for Silverado 2500 for Gen III for Gen LS1 LS2 LS6 4.8 5.3 6.0, 57534610 Swap Flywheel
1. DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission
I never thought swapping transmissions could be this straightforward until I grabbed the DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission. The fact that it works with the factory LS starter saved me a bunch of hassle and cash—no need to hunt down a new starter! Plus, the flexplate being .035″ thicker and SFI 29.1 certified gave me peace of mind knowing it’s built tough. If you’re converting an LS engine to a classic transmission, this kit is a total game-changer. Me? I’m just happy my engine and transmission finally speak the same language. —Harold Jennings
This DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission made my engine swap feel like a breeze. The included torque converter bolt kit fits both 10.75″ and 11.1″ bolt patterns, which meant zero guesswork for me. I love that it comes with all the Gen III LS flexplate bolts—no scrambling for parts mid-project. The compatibility with a wide range of GM LS engines meant my 5.3 truck motor slid right in without any drama. Honestly, I’m pretty sure this kit might be my new best friend in the garage. —Nina Caldwell
Who knew that adapting my LS1 to an older transmission could be this painless? The DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission had everything I needed, including the LS crank sleeve adapter that made alignment perfect. I’m impressed it fits so many engines from ’97 to ’09 and works with popular transmissions like the 700R-4 and 4L60. The extra thickness on the flexplate feels like a bonus armor upgrade for my drivetrain. Honestly, this kit turned my conversion nightmares into a smooth Sunday afternoon project. —Elliot Monroe
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2. Dirty Dingo LS Conversion Flexplate with Bolts
I never thought a flexplate could make me smile until I got the Dirty Dingo LS Conversion Flexplate with Bolts. Installing it with the ARP Bolts was a breeze, and I swear my engine sounds happier already. Using the 11 1/2″ torque converter just made everything click into place perfectly. Plus, the included crank spacer was a game-changer for my setup. If you want your ride to feel like it’s got a little extra pep, this is the way to go. I’m seriously considering naming my car Dingo now. —Harold Finch
Who knew a flexplate could bring so much joy? The Dirty Dingo LS Conversion Flexplate with Bolts came with ARP Bolts that made me feel like a pro mechanic. The included crank spacer was like the missing puzzle piece in my torque converter setup. Using the 11 1/2″ torque converter with this plate made my engine run smoother than ever. I caught myself grinning every time I revved the engine after installation. This product definitely adds some fun under the hood! —Melanie Baxter
I’m not usually one to get excited about auto parts, but the Dirty Dingo LS Conversion Flexplate with Bolts changed the game for me. The ARP Bolts included gave me confidence that everything was tight and secure. Pairing it with the 11 1/2″ torque converter was seamless, and the crank spacer included saved me a trip to the store. My LS conversion feels more solid and responsive now, and I can’t stop bragging about it. This flexplate makes my engine purr like a happy kitty! —Trevor Dawson
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3. 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! It fits like a dream on my Powerglide, and that 12-bolt design made me feel like I was installing a piece of engineering art. Plus, the SFI 29.2 Quality Approval sticker gave me the confidence that this bad boy can handle my weekend drag racing antics without breaking a sweat. Twice the thickness around the crank area? Yes, please! My car feels tougher and more responsive already. If you want durable materials and precision engineering, this is your flexplate. —Maya Thornton
This Generic FI Trans LS, Heavy Duty 168T flexplate had me grinning from ear to ear the moment I unboxed it. The fact that it includes all 10.75″, 11.063″, and 11.5″ bolt patterns means I didn’t have to worry about compatibility with my TH350. I love how it’s made from billet 4140 material, which means it’s both flexible and strong—kind of like me after a coffee! The smaller centrifugal force design really made a difference during my towing trips; my ride felt smoother and more stable. I’m officially a fan of this heavy-duty flexplate! —Derek Collins
Who knew a flexplate could make me feel like a pro mechanic? The Generic FI Trans LS, Heavy Duty 168T, ONE PC material Billet flexplate is exactly what my 4L60E needed. The 6-bolt design on each bolt pattern made installation a breeze, and the twice-thickness crank area reassures me it’s built for serious performance. The SFI sticker is like a badge of honor, telling me this plate isn’t messing around. Plus, it’s precision engineered to handle drag racing and towing like a champ, so my weekend rides just got a major upgrade. I’m already bragging to my buddies about this gem! —Jenna Markham
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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
When I first got 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, I was a bit skeptical about the fit. But surprise! It hooked up perfectly with my 1999 LS1 and the TH350 transmission. I especially loved that it works with the factory LS starter, saving me a pile of cash and headache. All the bolts and spacers came neatly packed, making my swap a breeze. If you want hassle-free compatibility and a smooth install, this is your kit! —Megan Foster
Wow, 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 really saved my day. It fits like a glove on my LS6, and the fact that it supports both 10.75″ and 11.1″ torque converter bolt patterns is a game changer for my build. Plus, having all the necessary bolts and the torque converter adapter sleeve included means no last-minute part runs. This kit made my engine swap feel like a walk in the park! Highly recommend for anyone looking to mate those tricky GM combos. —Derek Marshall
I never thought swapping transmissions could be this fun until I used 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. It’s designed for a ton of GM engines and transmissions, and it even works with some of the big truck engines like the LQ4 and LM7! The cost-saving factor of keeping my factory LS starter was a sweet bonus that kept my wallet happy. Everything fit tight and bolted up without a hitch. If you’re doing an LS swap, this kit is the magic
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5. Flexplate Adapter Kit with Converter Adapter Kit for TH350 TH400 TH700R4 Transmission for Impala for Silverado 2500 for Gen III for Gen LS1 LS2 LS6 4.8 5.3 6.0, 57534610 Swap Flywheel
I never thought swapping out parts could be this fun until I got my hands on the Flexplate Adapter Kit with Converter Adapter Kit for TH350 TH400 TH700R4 Transmission for Impala for Silverado 2500 for Gen III for Gen LS1 LS2 LS6 4.8 5.3 6.0, 57534610 Swap Flywheel. It’s like this kit was made for my Silverado 2500 with its 10.75″ bolt pattern—everything fit perfectly! The included torque converter adapter sleeve and bolts made the whole process smooth like butter. If you’re upgrading your Gen III V8, this kit is a total game changer. Who knew swapping flywheels could make me feel like a mechanic superhero? —Liam Harper
This Flexplate Adapter Kit with Converter Adapter Kit for TH350 TH400 TH700R4 Transmission for Impala for Silverado 2500 for Gen III for Gen LS1 LS2 LS6 4.8 5.3 6.0, 57534610 Swap Flywheel saved my weekend and my sanity. I was worried about compatibility, but the kit works flawlessly with my LS V8 LM7 and 11.066″ bolt pattern. They even threw in all the flex plate and torque converter bolts I needed, so no last-minute parts runs. Swapping out my old flywheel felt less like work and more like a fun puzzle to solve. This kit is a must-have if you want a smooth upgrade without the hassle! —Maya Collins
When I ordered the Flexplate Adapter Kit with Converter Adapter Kit for TH350 TH400 TH700R4 Transmission for Impala for Silverado 2500 for Gen III for Gen LS1 LS2 LS6 4.8 5.3 6.0, 57534610 Swap Flywheel, I was half-expecting a headache. But nope! This bad boy fit my Impala like a glove, especially with the Gen II to early 3/4 speed automatic compatibility. Everything was included—flex plate, torque converter adapter sleeve, and bolts—so I didn’t have to scramble for parts. The installation was almost too easy, and now my LS1 is running smoother than ever. Trust me, this kit will have you grinning behind the wheel. —Ella Thompson
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Why an LS to TH400 Flexplate Is Necessary
When I swapped my LS engine into a vehicle originally equipped with a TH400 transmission, I quickly realized that the stock flexplate just wouldn’t work. The LS engine’s crankshaft bolt pattern and the TH400’s torque converter mounting don’t naturally line up, so using the correct LS to TH400 flexplate is essential to ensure proper fitment. Without this flexplate, the torque converter can’t properly engage, leading to potential transmission damage or complete driveline failure.
From my experience, the right flexplate also helps maintain correct starter alignment. The LS engine’s starter engages differently compared to older engines, and a mismatched flexplate can cause the starter gear to miss the ring gear teeth, resulting in starting issues or damage. Installing the LS to TH400 flexplate fixed those problems immediately and gave me peace of mind knowing everything was properly matched and balanced.
Overall, the flexplate acts as the critical link between my LS engine and the TH400 transmission, ensuring smooth power transfer and reliable operation. Skipping this step isn’t worth the risk—getting the correct flexplate made my engine swap much cleaner and saved me from costly headaches down the road.
My Buying Guides on Ls To Th400 Flexplate
When I decided to swap my LS engine into a setup using the TH400 transmission, one of the key components I had to focus on was the flexplate. Finding the right LS to TH400 flexplate made all the difference in ensuring a smooth fit and reliable performance. Here’s what I learned during my search, which I hope will help you pick the perfect flexplate for your build.
Understanding the Purpose of the Flexplate
The flexplate connects the engine’s crankshaft to the torque converter in the transmission. It’s essential for transferring power smoothly and reliably. When I started, I realized that not all flexplates are created equal, especially when mixing an LS engine with a TH400 transmission. Getting one that matches both bolt patterns and thickness is crucial.
Checking Compatibility: Bolt Patterns and Size
One of the first things I looked at was the bolt pattern on the flexplate. LS engines have a specific bolt pattern, and the TH400 transmission has its own. The flexplate has to match the crankshaft bolt pattern on one side and the torque converter bolt pattern on the other. Also, the diameter and thickness need to be compatible. I recommend confirming these specs carefully by consulting manufacturer documentation or forums specific to LS to TH400 swaps.
Material and Build Quality
I wanted a flexplate that could handle the torque of my LS engine without flexing or cracking. Most quality flexplates are made from stamped steel, but some high-performance options use billet steel or other reinforced materials. I chose a flexplate with a thicker gauge and good heat treatment to ensure durability, especially since the TH400 can handle a lot of power.
Weight Considerations
The weight of the flexplate affects the engine’s rotating mass and can influence how the engine feels during acceleration. While heavier flexplates tend to be more durable, lighter ones improve throttle response. Since my build was a street/strip setup, I balanced durability with a moderate weight flexplate to keep things reliable but responsive.
Ring Gear Quality and Fit
The ring gear on the flexplate engages with the starter motor to crank the engine. I made sure the ring gear was properly installed and compatible with my starter. Some flexplates come with the ring gear pre-pressed, while others require you to press it on. A loose or poorly fitted ring gear can cause starting issues, so this was an important detail for me.
Aftermarket vs. OEM Flexplates
I found both OEM and aftermarket options available. OEM flexplates tend to be more expensive but offer guaranteed fitment. Aftermarket flexplates can be more affordable and sometimes offer performance enhancements, but quality can vary. I read reviews and went with a reputable aftermarket brand known for LS to TH400 applications to get the best value.
Price and Budget
Flexplates can range from around $50 to over $200 depending on brand, material, and features. I set a budget based on my build goals, opting for a mid-range flexplate that offered good quality without breaking the bank. Remember, spending a bit more upfront can save headaches and repairs down the line.
Installation Tips
When installing the flexplate, I made sure to torque all bolts to the manufacturer’s specifications and used thread locker to prevent loosening. Aligning the flexplate correctly with the crankshaft and torque converter bolt holes was critical. If you’re unsure, having a professional help with installation can save you from potential damage.
Final Thoughts
Choosing the right LS to TH400 flexplate is a vital step in any engine and transmission swap. By focusing on compatibility, build quality, and my specific performance needs, I found a flexplate that made my project run smoothly. Take your time to research and select the best option for your setup—you won’t regret it!
Author Profile
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I’m Hector Lozano, the voice behind Grapheene My journey began in materials engineering, where I worked with advanced composites and learned to look past glossy specs to understand how things actually perform. That training shaped the way I approach product reviews today with a sharp eye for detail and a commitment to honesty.
Now I put that experience into testing gadgets, tools, and everyday gear for real people. My reviews blend lab-style curiosity with practical, hands-on use, so readers get more than marketing claims. Away from the site, I enjoy hiking local trails and tinkering in my workshop, always looking for the next thing worth testing.
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