- 1964-1967 SP400 Parts Images
- How to wire the Switch Pitch on a Buick Transmission
    - 400 auto codes
- BOP Bellhousings and Automatic Identification
Results 1 to 9 of 9

Thread: Torque converter questions

  1. #1
    Join Date
    Sep 2012
    Location
    Binghamton
    Posts
    27
    Rep Power
    0

    Torque converter questions

    Well it seems something has come apart in my transmission. Im getting a whine that changes with RPM, some slipping and weird shifting. My guess is something is bad in the converter or the pump. Either way im going to be in the market for new tranny and converter, and im looking for some converter recommendations. My car is a 70 GS stage 1 clone. 430 with TH400. Engine is completely stock at the moment, howver I will be looking at power adders in the future. A cam will be in store, but certainly nothing radical. The car will be mainly street driven, with maybe a few passes down the track. The rear is the factory 8.2, and im not sure on gear ratio. Any insight is appreciated.

  2. #2
    Join Date
    Dec 2011
    Location
    SanFran CA
    Posts
    1,155
    Rep Power
    0
    For a street-driven TH400, I don't believe you can improve on the factory switch-pitch converter that was used in the 60s. It gives you the best of both worlds - high stall when you want it, and tighter hook up when you don't need all the extra revs, and of course much less heat going into the transmission oil.

    Now perhaps one of our resident transmission experts (which I'm not) can tell you what other parts you need to swap from a switch-pitch ST400 so the converter will fit/work.

    Ray

  3. #3
    Join Date
    Sep 2012
    Location
    Binghamton
    Posts
    27
    Rep Power
    0
    Ray, thanks for the reply. Im pretty certain the transmission in my car is a switch pitch tranny. I dont however believe that it works. I have a solenoid on my throttle linkage by the carb, that has 1 hot wire coming in, and 2 going down to the tranny. The engine in this car is 67 vintage and the guy I purchased the car from also said he believed it to be a switch pitch Th-400. Im not sure if any of this stuff is actually hooked up correctly, but the stall never seems to have changed that I could tell. I have checked that switch and there is power coming in, and power to the tranny on both of those wires at about 3/4 throttle.

  4. #4
    Join Date
    Dec 2011
    Location
    SanFran CA
    Posts
    1,155
    Rep Power
    0
    From your description, I think you probably have the 67 transmission which originally came with the engine. It should have 2 electrical connections, one for the converter and the other for downshift. If that's what you have, it means that the hard work has already been done for you. There should also be two switches on the throttle linkage. If you don't have both of them, one might have been lost when the engine was swapped into your A-body. You may need to look at a shop manual or a factory switch-pitch TH400 installation in order to find the other switch.

    The converter and downshift are both operated by solenoids. If you apply battery power to the connections, one at a time, you should hear the solenoids click if they are working. It will probably be easier to hear them if you do this when the engine isn't running. If the solenoids are good, check the switch (or the switch adjustment) on the throttle linkage before you go inside the transmission.

    Ray

  5. #5
    Join Date
    Sep 2012
    Location
    Binghamton
    Posts
    27
    Rep Power
    0
    Ok well some good news is I pulled the tranny pan, and found a piece of trash somewhat blocking my fluid pickup. I changed the filter and refilled with fresh fluid and the tranny seems fine. No more whining and its shifting good again. While I had the car jacked up, I have determined that it is certainly a switch pitch transmission. Now i need to figure out if its working or not. I remember reading about some guys wiring up the switch pitch to they're brake lights. Maybe ill dig into this a bit more tomorrow.

  6. #6
    Join Date
    Dec 2011
    Location
    SanFran CA
    Posts
    1,155
    Rep Power
    0
    I would say that's very good news. You just got out from under some potentially expensive repairs.

    Sorry, but I don't understand the point of wiring the switch pitch to the brake lights. However, you could wire it to a manual switch instead and find out very quickly whether it is working or not.

    Ray

  7. #7
    Join Date
    Sep 2012
    Location
    Binghamton
    Posts
    27
    Rep Power
    0
    Hey Ray. You were right about the one switch being left out when the transmission was swapped in. The only thing controlling the switch pitch at the moment is the one switch on the carb linkage that also controls the kickdown. From what I understand the switch pitch was originally controlled 2 ways. 1 is what I have now. It goes into high stall mode and kickdown for passing. The other way which im missing is a switch that would put it in high stall mode when your foot is off the throttle. My idea with the brake lights would be to have it in high stall at a stop light, but the more Ive thought about it, it would go right back into low stall as soon as you let off the brake, so that doesnt help the launch much. Im starting to lean towards your idea of a manual switch to control it when I want. Being wired the way it is, it no wonder why ive never felt it work. The switch pitch is only engaged in passing gear right now.

  8. #8
    Join Date
    Dec 2011
    Location
    SanFran CA
    Posts
    1,155
    Rep Power
    0
    The original idea behind the closed-throttle switch was to reduce creep when the engine was idling in gear. I don't know how necessary that was with a stock engine, but its real advantage is when you have a modified engine that has a higher idle speed than stock.

    This is another reason why I feel the SP converter is such a good choice behind a modified engine that will mainly be street-driven.

    Ray

  9. #9
    Join Date
    Sep 2012
    Location
    Binghamton
    Posts
    27
    Rep Power
    0
    I did some testing today and the converter works. I wired it up to a 3 way toggle switch. 1 way keeps in it high stall, the other way high stall with your foot on the brake, or the middle position leaves it in low stall. Now its time to go play and see how this thing acts.

Similar Threads

  1. Dynaflow torque converter
    By LONG in forum Transmissions and Drivelines...
    Replies: 5
    Last Post: 03-12-2013, 06:46 PM
  2. Torque converter
    By Seamus UK in forum Transmissions and Drivelines...
    Replies: 2
    Last Post: 05-03-2011, 05:24 PM
  3. picking a torque converter?
    By 67buickss in forum Big Block: 400, 430, 455
    Replies: 6
    Last Post: 08-16-2009, 12:34 PM
  4. 62 torque converter
    By lentzjj in forum Transmissions and Drivelines...
    Replies: 9
    Last Post: 07-16-2009, 02:42 PM
  5. torque converter, or tranny?
    By RonLange in forum Transmissions and Drivelines...
    Replies: 2
    Last Post: 04-24-2005, 08:17 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
TeamBuick.com Privacy Policy