The TH400 (ST400) was made with the nailhead pattern for 3 years- 64, 65, and 66. Or so I thought. Apparently AMC contracted GM to make a 400 with the nail pattern from 1969-73. They installed them in some models with an adapter ring for their engines. I just purchased one with a 1972 build date. Who knew? That gives us some additional options other than the 1964 one year only model and the hard to find 65-66 switch pitch.
Does the later nailhead have a different bellhousing bolt pattern than the earlier ones? I have a 55 322. Thanks, Rich
I have what I think is a 64 ST400 with BN-64-37000 on the nameplate then 553 is also stamped there. When I bought it and shipped it here I didn't realize that it was one year only model. What is the difference between 64 and the later ones and will a standard rebuild kit be OK?
Most of the mechanical rebuild parts are the same, 64 has a unique 1 year only valve body. They have the same three speeds, but the shift arm doesn't have 1st gear provision. Just second and third. Be careful taking valve body apart, i think the gaskets are hard to find.
That tag number is a 64 ST400. @38Chevy454 is correct, a one year only valve body. The fluid paths in the case also match that valve body, so later valve bodies will not work. While it does have all 3 speeds, the shift has only the provisions for D and L. All the rest of the internals are the same as the later ones. Fatsco has the rebuild kits for the 64, including the correct valve body gaskets. It also only has 4 check balls instead of the normal 6 and uses an impossible to find sprag instead of a roller clutch in the output section. That year model (and a few years more) used a smaller extension housing bushing and slip yoke. The bushing is available from CTPowertrain.
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