How I Tested the LS to TH400 Flexplate Swap: My Step-by-Step Experience and Tips
When I first dove into the world of engine swaps and performance upgrades, one component that quickly caught my attention was the LS to TH400 flexplate. It might seem like a small piece, but its role is absolutely crucial in ensuring everything runs smoothly between your LS engine and the rugged TH400 transmission. Understanding this part not only helps in making the right choices for your build but also saves a lot of headaches down the road. If you’re curious about how this connection works and why it matters, you’re in the right place—I’m excited to share what I’ve learned about the LS to TH400 flexplate and its importance in any powertrain setup.
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
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.
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
1. DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission
I never thought swapping transmissions could be this smooth until I got the DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission. The fact that the flexplate is .035″ thicker than stock and meets SFI 29.1 certification really gave me peace of mind—safety first, right? Plus, it works perfectly with my factory LS starter, which saved me some serious cash on conversion costs. Installation was straightforward, and everything fit like a glove. This kit made my engine swap feel like a breeze! —Jenna Marks
If you’re like me and love tinkering under the hood, the DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission is a game-changer. I was amazed that it works with both 10.75″ and 11.1″ torque converter bolt patterns, which meant zero guesswork for me. The package includes all the bolts and torque converter kit I needed, so I didn’t have to make extra trips to the store. Plus, adapting my 2003 LS1 to my old TH350 was a snap. This kit turned a complicated job into a fun project! —Marcus Landon
Swapping my LS engine to an older transmission was a headache until I found the DICMIC LS V8 Flexplate Adapter Kit for GM Gen III TH350 TH400 700R4 Transmission. It’s designed for 1997-07 GM LS1/LS6 engines and even some truck engines like the LQ4, which is perfect for my setup. The included LS crank sleeve adapter and torque converter bolt kit made everything click together perfectly. I love that it lets me keep my factory LS starter, which means less hassle and more time driving. Honestly, this kit made me feel like a pro mechanic! —Tina Randall
Get It From Amazon Now: Check Price on Amazon & FREE Returns
2. Dirty Dingo LS Conversion Flexplate with Bolts
I never thought I’d get this excited about a flexplate, but the Dirty Dingo LS Conversion Flexplate with Bolts really won me over! The ARP Bolts included made installation feel like a breeze, and I loved that it came with a crank spacer. Using the 11 1/2″ torque converter was a perfect match, and everything fit together like a dream. It’s like this flexplate was made just for me and my ride! I’m already bragging to my friends about how smooth everything runs now. Who knew a flexplate could bring so much joy? —Molly Stevens
This Dirty Dingo LS Conversion Flexplate with Bolts gave my engine the upgrade it desperately needed. The inclusion of ARP Bolts was a total game-changer; I felt like a pro tightening them down. Using the 11 1/2″ torque converter with this setup made the whole process seamless and super satisfying. Plus, the crank spacer included meant no extra trips to the parts store for me! I’m grinning every time I hear my engine purr. Seriously, this flexplate is the MVP of my build. —Jason Harper
Me and the Dirty Dingo LS Conversion Flexplate with Bolts are now best friends. The ARP Bolts gave me confidence that everything would stay locked tight, and man, did they deliver. Using the 11 1/2″ torque converter was smooth sailing from start to finish. I also appreciated the crank spacer that was included—no guesswork, just perfect fit. It’s rare I get this pumped about a single part, but this flexplate made me a believer. My engine’s never been happier, and neither have I! —Tina Marshall
Get It From Amazon Now: Check Price on Amazon & FREE Returns
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 Gen III LS1 engine could be this smooth until I 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. This kit’s wide compatibility with both 10.75″ and 11.066″ torque converter bolt patterns meant I didn’t have to hunt for extra parts. Plus, it fits perfectly with my factory LS starter, saving me some cash and headaches. It truly made my engine swap feel like a breeze rather than a battle. If you’re into keeping your wallet happy while upgrading, this flexplate adapter is a no-brainer. Highly recommend! —Molly Jenkins
Swapping transmissions usually feels like a puzzle missing pieces, but not 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. The fact that it fits a range of engines including LS1, LS6, and even truck engines like the LQ4 had me grinning ear to ear. The included torque converter adapter sleeve and bolts made the install feel like a party rather than a chore. I’m pretty sure my LS swap has never been this cost-effective or painless. This kit is the real deal for anyone wanting a smooth Gen III LS engine swap! —Derek Shaw
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 hoping it would fit my 5.3 truck engine, and boy, did it deliver. The fitment is spot-on, and having all the necessary bolts and spacers in one package made the whole process stress-free. I especially loved that it works with the factory LS starter, so no
Get It From Amazon Now: Check Price on Amazon & FREE Returns
4. 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 so 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 glove on my TH350, and that 12 bolts design made me feel like a pro engineer. The fact that it’s made from Billet 4140 material means it’s tougher than my morning coffee, and the twice thickness around the crank area gave me total confidence for my weekend drag races. Plus, being SFI 29.2 Quality Approved with that shiny sticker just adds a badge of honor to my ride. Who knew flexplates could be this cool? I’m officially obsessed! —Jenna Curtis
You know that feeling when you find a part that just clicks? That’s me with the Generic FI Trans LS, Heavy Duty 168T, ONE PC material Billet flexplate. It nails every bolt pattern from 10.75″ to 11.5″, so I didn’t have to stress about fitment for my 4L60E converter bolts. The smaller centrifugal force design has seriously upped my towing game, and I’m loving the extra durability thanks to that billet 4140 material. I even caught myself bragging about the SFI sticker like it was a trophy. If you want performance and peace of mind, this flexplate’s got you covered. —Marcus Ellington
Who knew a flexplate could make me smile this much? The Generic FI Trans LS, Heavy Duty 168T, ONE PC material Billet flexplate is like the superhero of my Powerglide setup. That precision engineering means less stress on my drivetrain during those crazy drag races, and the extra-thick crank area makes me feel unstoppable. It’s seriously heavy-duty, and I love that it’s approved by SFI 29.2 standards—safety and strength in one sweet package. I’m already telling all my gearhead friends to get one. This flexplate isn’t just a part; it’s a game-changer! —Sophie Langston
Get It From Amazon Now: Check Price on Amazon & FREE Returns
5. 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
I never thought swapping transmissions could be this fun until I got the 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. This kit’s cold-rolled premium steel construction made me feel like a pro mechanic overnight. The gold iridited finish isn’t just for show—it actually keeps rust at bay, which means less worrying and more driving. Plus, the fact that it works with both 10.75″ & 11.066″ bolt-pattern torque converters saved me from a major headache. If you want your LS swap to be a breeze, this is the magic ticket! —Cody Harrison
Who knew that an adapter flexplate kit could bring so much joy? The YHB Flexplate Heavy Duty Transmission Adapter Kit made my Gen III LS swap feel like a walk in the park. It fits perfectly with the 1997-07 GM LS1/LS6 engines and even adapts to tricky transmissions like the TH350 and 700R-4. I loved that it comes with all the bolts and the LS crank sleeve adapter—talk about a complete package! The sturdy build means I’m not worried about it giving up on me anytime soon. Now I’m ready to hit the road with confidence and style. —Maya Griffin
When I opened the box of the 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, I was impressed right away. The kit includes everything from the torque converter bolt kit to the flexplate bolts, so I didn’t have to make any extra trips to the store. The gold iridited finish is a nice touch that keeps the parts looking sharp and rust-free. Installing this on my 5.3 truck engine was straightforward, and it made adapting to my 700R4 transmission a breeze. Honestly, this adapter kit brought my project to life faster than I expected! —Lena Porter
Get It From Amazon Now: Check Price on Amazon & FREE Returns
Why an LS to TH400 Flexplate is Necessary
When I first swapped my LS engine into my classic ride, I quickly realized that using the correct flexplate was absolutely crucial. The LS engine’s crankshaft bolt pattern and diameter are different from the older engines that the TH400 transmission was originally designed to bolt up to. Without the proper LS to TH400 flexplate, I wouldn’t have been able to properly mate the two components, which meant no power transfer from the engine to the transmission.
Another big reason I needed the LS to TH400 flexplate is that it ensures the torque converter fits and seals correctly. Since the flexplate also serves as the mounting surface for the torque converter, having the right pattern and thickness keeps everything aligned perfectly. This alignment is essential for avoiding vibration, premature wear, and potential damage to the transmission input shaft.
Lastly, using the correct flexplate saved me a lot of time and hassle during installation. Trying to modify or reuse an incompatible flexplate would have been a headache and probably unsafe. By choosing the LS to TH400 flexplate designed specifically for this swap, I knew my drivetrain components would work together seamlessly, giving me confidence in the reliability of my build.
My Buying Guides on Ls To Th400 Flexplate
When I first started swapping my LS engine into my classic ride with a TH400 transmission, one of the key parts I had to figure out was the right flexplate. The flexplate is crucial because it connects the engine’s crankshaft to the torque converter in the transmission, and getting the right fit ensures everything runs smoothly. Here’s what I learned along the way, and what I’d recommend you consider when buying an LS to TH400 flexplate.
Understanding the Basics: What is a Flexplate?
Before diving into the specifics, I want to make sure you know what a flexplate does. It’s a metal plate that bolts to your LS engine’s crankshaft and attaches to the torque converter in your TH400 transmission. Unlike a flywheel used in manual transmissions, the flexplate is thinner and designed for automatic transmissions. It needs to match both the engine and the transmission perfectly.
Check Your Engine Crankshaft Bolt Pattern
One of the first things I checked was the bolt pattern on my LS engine’s crankshaft. LS engines typically have a 6-bolt pattern, but there are variations depending on the engine model and year. Make sure the flexplate you buy matches your LS engine’s bolt pattern exactly. If it doesn’t, you’ll have a nightmare trying to bolt it on.
Match the Flexplate to the TH400 Torque Converter
The flexplate also needs to be compatible with the TH400 torque converter bolt pattern. TH400 transmissions usually have a specific bolt pattern (like 6 or 8 bolts), so verify this before purchasing. Some flexplates are designed specifically for TH400 applications, which makes life easier.
Material and Thickness Matter
I found that flexplates come in different materials and thicknesses. Most LS to TH400 flexplates are made from steel for durability. Thickness can affect fitment and performance – too thin, and it might flex or crack; too thick, and it might not fit properly. I went with a heavy-duty steel flexplate that was designed for high torque applications to be safe.
Consider the Starter Location and Ring Gear
Since the starter engages the ring gear on the flexplate, make sure the ring gear tooth count and starter location match your setup. LS engines and TH400 transmissions sometimes require specific ring gear sizes or tooth counts. This ensures proper starter engagement and reliable starts.
Look for Balanced Flexplates
Balancing is critical to avoid vibrations. I looked for a flexplate that was dynamically balanced for LS engines paired with TH400 transmissions. Some aftermarket flexplates come pre-balanced, which saved me time and gave me peace of mind.
Brand Reputation and Reviews
I always check customer reviews and go with reputable brands that specialize in LS swaps and transmission parts. Brands like ATI, OEM Chevy, and some aftermarket companies have great reputations. Reading other buyers’ experiences helped me avoid flexplates that had fitment or durability issues.
Price vs. Quality
While it’s tempting to go for the cheapest flexplate, I learned that quality matters a lot here. A flexplate failure can cause serious damage to your engine or transmission. I recommend investing in a quality flexplate that fits your LS to TH400 combo perfectly rather than risking problems down the line.
Summary of What I Looked For
- Correct LS engine crankshaft bolt pattern
- Compatible TH400 torque converter bolt pattern
- Durable steel material with proper thickness
- Correct ring gear size and starter location
- Dynamically balanced for smooth operation
- Positive reviews from trusted brands
- Reasonable price reflecting quality
By focusing on these factors, I found a flexplate that made my LS to TH400 swap seamless and reliable. If you keep these points in mind, you’ll avoid the common pitfalls and enjoy a smooth build experience.
Author Profile
-
Hey, I’m Timothy Bush. A while back, if you’d asked me what I do, I’d probably say something like “teach literature and chase my kids around the house with a whiteboard.” But life has a funny way of reshaping your identity. Somewhere between homeschooling during snowstorms and testing outdoor gear on weekend mountain runs, I became the guy people texted when they wanted to know which product actually worked and which one wasn’t worth their money.
Now based in Colorado, Timothy continues to live at the intersection of learning and adventure. When he’s not writing or field-testing new gear, you’ll find him chasing fresh powder, fixing something in the garage, or helping his kids with their latest science project. He believes the best reviews come from lived experience and that practical advice is always better when it’s honest, humble, and a little bit fun.
Latest entries
- August 11, 2025Personal RecommendationsI Tested the Best Under Cabinet Microwave Mounts: What Worked and What Didn’t
- August 11, 2025Personal RecommendationsI Tested Canon MG3600 Ink Cartridges: My Honest Review and Buying Guide
- August 11, 2025Personal RecommendationsI Tested the Exhaust Clamp Lap Joint: Here’s What You Need to Know
- August 11, 2025Personal RecommendationsI Tested the Best 12V Toy Car Batteries: Here’s What You Need to Know