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adapting the 400/300 trans to 57-63 engines

Updated: Jun 4, 2021

the 400 and 300 transmissions are the best bang for your buck swap to ditch the dynaflow. the bellhousing is the same pattern for all 57 to 66 364/401/425. we sell every part for the swap, pictured below. no matter what, you will need the bushing to center the converter in the crank. if you have a 59 to 63 401 or 425, you can grind the lip off the back of the dynaflow crank before tapping in the converter centering bushing and just use a 64 to 66 stock flexplate. some '65 flexplates and all '66 have the dual coverter bolt pattern for the 300 smaller converter and 4l60e swap. take note that you cannot use the 64 to 66 stock flexplate on a 364 due to wrong counter balance. also take note whether your engine has been rebuild and weight was added or removed to the previous triangular stock dynaflow flexplate. that counter balance will have to be matched at your machine shop (not a big deal.) otherwise, shown below, we sell the late style flexplate for the swap, with a larger hole in the middle for dynaflow crank, if you don't want to grind the lip off the crank, or you've got a 364. you can use the 64 to 66 starter on the 61 to 63 blocks. otherwise we sell a dynaflow starter spacer to use the original dynaflow starter with the 400/300. take note that when using the starter spacer on 61 to 63 blocks, you will have to cut off a casting fixture nub off, which stems off the head gasket surface, for clearance. otherwise we sell mini starters for all applications. 57 to 60 are the same starter bolt pattern before it changed in 61. be aware that with doing any trans swap on 60 and earlier buicks, will require a rear suspension fab with a 2 link or 4 link to eliminate the torque tube. triangular four link is ideal with air bags and provides the least amount of pinion angle change through suspension travel and theres no track bar to pull the body from left to right through travel. . otherwise a chevy truck trailoring arm set does the trick and you can recycle your spring saddles and track bar. recycling the column shift and getting the ratio right and perfect is a little time consuming but not hard. if insisting on floor shift, check out Gennie shifter. as far as having a driveshaft made, its always cheaper to get a drive shaft that's too long and have it shortened, than to make one longer, or have one made from scratch (can cost 3 times as much). prices on parts are not listed in this section as they may change as time progresses. please check out parts section of website, or just call us 530 272 1564

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