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So I have a rebuilt TH400 automatic I plan on using to replace a TH350 which is currently paired up with my 454 motor. Do I need to consider upgrading anything else when I do this swap or will all other components work properly (fly wheel, torque converter, drive shaft, etc) Any advice you can give would be very helpful. The casting number on the 454 is 361959

Thanks,

Will
 

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400 converter has a bigger bolt circle. Since a 454 wasn't available with a TH350 , something has been done to the flywheel already. The 350 converter will fit the 400 and offers a little more stall , if you're not running a hp converter
 

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You're gonna need a different driveshaft. TH350 trans is shorter than a 400 and the output shafts are different sizes too.
 

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It's called a flex plate guys, not a flywheel and the stock ones aren't very strong, good time to upgrade the flex plate.

Yes you will also need a new driveshaft and yoke for the turbo 400.

You might also want to swap out the yoke on the pinion gear and build that new drive shaft using 1350 U-joints front and back.
 

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Alot of replacement flexplates are drilled for both patterns but you can reuse your th350 converter and then you knkw it will bolt on what you have. My stock th400 drivesbaft out of a 69 chevelle is 54.5 inches center to center of the u joints. My 70 driveshaft for a th350 is 55.5 inches so your looking at cutting the shaft about a inch. But measure before cutting. When i swapped in a th400 in my el camino. The driveshafts were a inch different too. Jim
 

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It's called a flex plate guys, not a flywheel and the stock ones aren't very strong, good time to upgrade the flex plate.

Yes you will also need a new driveshaft and yoke for the turbo 400.

You might also want to swap out the yoke on the pinion gear and build that new drive shaft using 1350 U-joints front and back.
picky picky picky
 
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