Stage 1 Switch Pitch

Discussion in 'The "Juice Box"' started by BA, Jan 26, 2014.

  1. BA

    BA Well-Known Member

    I have a 70 stage 1 trans and I am considering converting it to a switch pitch (I have a donor trans) and just need a confirmation that this can be done. I know that I will need a S.P.converter and switch as well as the case restrictor plug. Will this change over affect the regular operation other than the dual stall? Any thoughts?
  2. DaWildcat

    DaWildcat Platinum Level Contributor

    Bill, you'll need the following:

    VP converter
    VP pump w/VP solenoid
    VP input shaft
    Case orifice
    Dual terminal case electrical connector
    Means of activation

    Depending on if you choose to use the ST400 converter or smaller ST300 converter, you may find low stall is a few hundred rpm lower than what you're used to in a fixed pitch converter. If that causes problems with idle quality, you then may want to activate high stall at idle like the factory did. Other than that you should notice no other changes in operation.

    Hope that helps...

  3. BA

    BA Well-Known Member

    Hi Devon,

    I knew I forgot about something. Pump and shaft assem. Will shift quality still be there? 3 to 1? Idle quality is already poor so SP convertor should help.
  4. DaWildcat

    DaWildcat Platinum Level Contributor

    The shift behavior will stay the same as you'll be retaining the original "BB" valve body.

    You'll love it, by the way!

  5. rmstg2

    rmstg2 Gold Level Contributor

    I have the high stall activated off of the brake light switch. As Devon said you will love it.:TU:

    Bob H.
  6. BA

    BA Well-Known Member

    Thanks guys,

    Now who's shift kit should I use?
  7. DaWildcat

    DaWildcat Platinum Level Contributor

  8. Jim Weise

    Jim Weise 1000+HP

    Get the 400 1-2 kit from Trans go, drill the A and B orifices to .110, pink spring on the regulator valve, no springs on the 1-2 accumulator valve in the valve body, and omit the big 2-3 accumulator spring under the piston.

    Use a red stripe vacuum modulator.

    if the clutches aren't a mile wide in the trans, it will provide a quick shift you have a hard time feeling at light throttle, but will chip the tires at WOT if you have enough grunt and gear in it. Adjustment of the vacuum modulator will give you the right shift feel and timing under light throttle.

    You should also put the big snap ring on the intermediate clutch that comes with the kit.

    I have the modified 300 SP converters available.

    Good luck

  9. 71GSX455-4SPD

    71GSX455-4SPD Nick Serwo Magic Car

    Jim, you have converters available???
  10. Jim Weise

    Jim Weise 1000+HP

    Yup, yours in in process as we speak.

  11. BA

    BA Well-Known Member


    What do you typically charge for a converter?
  12. 71GSX455-4SPD

    71GSX455-4SPD Nick Serwo Magic Car

  13. Jim Weise

    Jim Weise 1000+HP

    The Variable Pitch 12" converters are $399 with a $100 core charge.


    BRUCE ROE Well-Known Member

    Will you also rebuild 13" switch pitch cores? I have MANY. Bruce Roe
  15. Jim Weise

    Jim Weise 1000+HP

    Sure Bruce, no problem.

  16. 71GSX455-4SPD

    71GSX455-4SPD Nick Serwo Magic Car

    Bruce, are you still making time delay boxes for the switch pitch? I had read that a while ago...

    BRUCE ROE Well-Known Member

    Ken Lisk, There are a couple of those on the shelf; not much demand this season.
    The factory control
    only worked at
    idle or near full throttle. Mine was developed to increase drivability on the street, in the mid range where
    most driving
    happens. It has torque sensing and timers for smoother shifts, fewer downshifts, and more zip. There is one
    "maximum performance" mode
    available. I'll post the flow diagram here; however, it probably makes a lot more sense
    when your are driving, than just reading it. Bruce

    Attached Files:

  18. 71GSX455-4SPD

    71GSX455-4SPD Nick Serwo Magic Car

    Thanks Bruce, I was actually able to follow that fairly well! I would be interested in one to go with the converter Jim is building for me. Could you PM me with cost, etc.? I don't want to hijack the thread. Thanks!
  19. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I have Bruce's SP controller. I have found that the high stall of that 12" converter is too loose for my taste when starting out from a dead stop. Bruce's controller in it's as delivered state has no way to reduce the time from "brake on" high stall to low stall below 3.2 seconds. As a result, when you release the brake to accelerate away from a stop, the converter is in high stall for no less than 3.2 seconds. I sent my controller back to Bruce and had him modify it so that it would go directly to low stall after you released the brake. There are other timers built into the box for drag racing. Those you can adjust, but for street driving, I found that modification helpful. You may want to consider that. I detailed all this in a thread sometime ago.

    Here it is Ken,

    BRUCE ROE Well-Known Member

    The starting point here was a great cruiser, with 13" converter and 2.41:1 axle for low rpm
    and economy. The switch pitch restored a lot of performance while maintaining (maybe even
    increasing a point) fuel economy. A by product was much smoother operation. The car gets
    to all 4 borders from time to time. If your care for none of that, instead racing, there may
    still be a controller mode to suit. There are other, simpler ways to control a drag car converter.

    Bruce Roe

Share This Page