Info on B&M universal kickdown switch

Discussion in 'The "Juice Box"' started by Dragdoc, Apr 22, 2020.

  1. Dragdoc

    Dragdoc Well-Known Member

    Hi all, I converted my torque tube and dynaflow equipped ‘60 LeSabre to a ‘66 st400 and driveshaft.

    The car never had a kickdown switch and it seems that later factory switches only function at full throttle input. Something that operated kickdown over a range of, say, 75-100% throttle input makes more sense to me.

    So, is anyone familiar with B&M universal kickdown switch #20297? The description is kinda vague regarding operating range and the phone “tech” was reading out of the catalog.

    Also open to other suggestions - custom fab work is fine if need be. Thanks!
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Kick down is accomplished electronically, so it is just an off and on of 12 volts to the electrical connection on the side of the transmission. The hardest part will be to figure out how to mount it so it activates when you want it to. The switch pitch valve bodies also lacked a 3-2 valve, so they usually only kick down at close to full throttle. When I had my switch pitch, I swapped in a later (1971 BC) valve body. That gave me a hydraulic part throttle kick down at lower speeds as well as the ability to use the much more common flat filter.

    http://www.buickperformanceclub.com/SPTrans.htm
     
  3. 1969RIVI

    1969RIVI Well-Known Member

    Not to side track your thread Dragdoc, but I got a related question. The th400 in my 69 Riv has the kick down switch terminal sicking out the side of it but it's not hooked up, matter of fact I didn't even see a wire hanging anywhere under the car for it to go to the switch. Is there any reason why someone would have disconnected it? Any gains of any kind by not having it? Does not having it hurt the trans in anyway?? Thanks for letting me piggy back in this thread if it's not wanted let me know and I'll delete my post.
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Without the kick down connected, the transmission will short shift at WOT. It will not hurt the transmission to not have it, but why would you not want it? It's easy to run your own wire. Just find the switch at the gas pedal, make sure it has power to it, and run a wire to the transmission. All it does is pass 12 volts to the transmission when it closes. One side gets key on 12 volts, the other side goes to the transmission.
     
  5. 1969RIVI

    1969RIVI Well-Known Member

    Thanks Larry I'm gonna look for or run a new wire. It's strange that someone removed it?? What do you mean exactly by short shift at WOT? it will shift at lower rpm's or shift quicker/sooner than it should?
     
  6. gsgtx

    gsgtx Silver Level contributor

    the switch pitch 2-speed 300 will go to high stall at 60% throttle, am sure the switch pitch 3-speed 400 is the same at 60%.
     
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    It's probably there, it comes off the engine harness at the firewall. It may have been cut at some point or just broken. We are talking about a 50 year old car of which you are not the original owner. The engine probably has been changed a number of times. Still think it is strange that it's missing?:D




    Same thing. If the kick down is not operational, the WOT shift points will be much lower, by several hundred RPM. When I took my car to the track last year, I swapped carburetors at the track. I put the 1000 DP on, and made a couple of runs before I realized that the transmission was shifting at about 5300 or less. It normally shifted at around 57-5800. Unfortunately, I had a fluid leak at the Gear Vendors that forced me to stop racing. Then it dawned on me. I had forgotten something. I hadn't raced the car in about 3 years, and I just forgot. When I swapped carburetors, I needed to put a piece of fuel line hose on the kickdown switch at the pedal. Due to the throttle throw being shorter with the 1000 DP, it wouldn't activate the switch at full throttle unless I slipped a piece of hose over the switch to build it up.:(:) The car still ran 11.60's:)
     
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  8. 1969RIVI

    1969RIVI Well-Known Member

    The car came to Canada with its original engine, guy before me spun a bearing, yanked out the original numbers 430 and scraped it and put this "rebuilt" 72 455 in. The guy that contacted me about doing the rebuild said he still had the original heads in his shop somewhere.

    As for that switch wire I gotta find it or run a new one as if I understand correctly it could have way more acceleration than it currently does and it's being "left on the table" so to speak. You're right they probably clipped it off doing the swap and never looked back.
     

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