ST400 S wap for ST300

6

64xp715

Team Member
I have a 1964 Riviera with a 425 nailhead and ST300. Since this is a one-off year for this tranny, I have been contemplating a swap. My current plan is to use a 1966 ST400 (code BR).
Now the questions. Is this a direct swap or will I need to modify the cross-member or driveshaft? Can I use the smaller torque converter from my ST300?

I’m new to the forum and to the intricacies of these cars. :wavey:
THANKS
 
The 64 Riv had a ST 400, but it was not a switch pitch like the 65-66 Nailhead ST 400. They are dimensionally the same size and bolt in the same location using the same mounts. The fixed pitch converter from the 64 ST 400 will not work in a later ST 400. The wiring will also be different. You will need the stator idle switch (for stator positioning at idle) and detent/stator switch (for downshifting and stator positioning under load). These can be found on any 65-67 Buick with a ST 400 or ST 300. You would just need to adapt then to your car using the same brackets or modifying them.
 
Thank you for the info. I will track down the switches and get it hooked up. I think that this will be a big improvement over the’64 setup.
 
I may be in a padded room before I understand this transmission. I have purchased an ST400 out of a ‘66 Wildcat 401. Code is BR so all seems good. This transmission was on a dolly when I bought it and the torque converter was separate. How do I identify the tc as a switch pitch? I don’t see any markings on it.
 
Thanks,
This is just what I needed. I’ve now confirmed that the TC is switch pitch and I’m ready to get it installed.
I think (hope) that I understand the wiring needed to complete the swap. Really looking forward to the improvements over the ‘64 transmission.:thumbsup:
 
Another question regarding the switches for this tranny. The switch on the drivers side is correct with 2 blades set at 90*. I understand that the top (horizontal) blade is is for the SP stator. I’m looking to use a 3-position toggle for it. The vertical blade is for the kick down. I have attached a pic of the kick down currently on my ‘64. Will this kick down work with the SP? If not, should I just get a B&M?
Finally (?), I am having the trans swapped at a local shop since I don’t have a lift and (at my age) it’s too much to do laying on my back. Can I drive it home (15 miles) without any wiring in place? My next project is a complete rewire.

Thanks:thumbsup:
 
The picture did not show up in the last post.

It will be OK to drive without transmission wiring hooked up. The only caution would be if you have to floor it, the extra kick from a downshift won't be there.
 
I would say use a push button interrupter switch to provide 12v to the kickdown for on demand response, instead of a toggle.
A separate toggle will do well for the Switch Pitch, I believe. I have a push button setup on my kickdown, and it works well for me.
I currently don't have the Switch Pitch installed, similar scenario. I have two ST300's here, one with SP, one without.
My SP tranny is in need of repairs, and I think that even if I did have it back to full operation; I would still keep the added little interrupter switch for fun.
It's nice to be able to kickdown without going full throttle. She still gives a nice surge of power with just a bit more gas, instead of pedal to the floor.
 
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