ST400 build

Discussion in 'The "Juice Box"' started by GMMADMAN, Apr 30, 2018.

  1. GMMADMAN

    GMMADMAN Well-Known Member

    I have a 67 short tailshaft ST400 that I'm about to tear down and rebuild to back my Stage 2 TA 455 street build. I have some parts that I've compiled together after reading alot of posts on upgrades to the ST400. I will be using an ST300 torque converter, newer style tailshaft & housing, Trans-Go 400-1&2 shift kit, & a mid 70's valve body. Which sprag do you guys recommend? Thanks
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  3. GMMADMAN

    GMMADMAN Well-Known Member

    Donuts & Peelouts likes this.
  4. Grandpas67

    Grandpas67 Well-Known Member

    Hey guys. What is the benefit of using the st300 torque converter over the 400? I have a spare laying around and can easily put it in my 67 gs400 as it's all apart right now for an engine rebuild.

    We're going to cruise this car and maybe do a little autox and or drag racing once in a while.
     
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The smaller a converter, the higher the stall is naturally without any internal modifications. I am assuming you are talking about the switch pitch transmissions?
     
  6. Grandpas67

    Grandpas67 Well-Known Member

    Yes, sorry. Switch pitch.
     
  7. Grandpas67

    Grandpas67 Well-Known Member

    how would the higher stall effect the switch pitch transmission?
     
  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    It doesn't affect the transmission, you get higher stall speeds. The ST400 13" converter has stall speeds of approximately 2100/1100. Put the ST300 12" in and it would be more like 2600/1400. This is behind a Buick big block. Jim Weise modifies the 12" ST300 converters to produce more like 3000/1800
     
    Grandpas67 likes this.
  9. the 300 converter is also lighter.
     
  10. Bens99gtp

    Bens99gtp Well-Known Member

    Your transaction should already have the smooth intermediate sprag. You shouldn't need to buy a full drum, just the sprag. I don't know what year they went to a roller sprag there, but those require a new drum.

    Your 67 tran's might even have the non roller sprag in the gear set that holds onto the center support. They went to a roller sprag in this location a few years b4 putting it in the intermediate location. The roller worked better in stk form than the 16 element sprag did but didn't allow upgrades........but I don't feel the roller sprag below the center support works better, but those that have a regular sprag down there were 32 or 36 elements not just 16
     
  11. BRUCE ROE

    BRUCE ROE Well-Known Member

    I have seen a 9 element roller broken; never a broken 16 element. Bruce Roe
     
  12. Bens99gtp

    Bens99gtp Well-Known Member

    The none roller sprays had more of a chance to slip, and flip over. The rollers physically can't flip. I honestly don't know how many rollers are in the roller sprags.....
     

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